Durable large and regulation weight golf ball incorporating foamed intermediate layer

ABSTRACT

Large diameter golf balls having at least one foamed intermediate layer are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 15/197,988, filed Jun. 30, 2016, which is a division of U.S. patent application Ser. No. 14/467,089, filed Aug. 25, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/145,648, filed Dec. 31, 2013, the entire disclosures of which are hereby incorporated herein by reference.

U.S. patent application Ser. No. 14/145,648 is a continuation-in-part of U.S. patent application Ser. No. 14/017,979, filed Sep. 4, 2013, now U.S. Pat. No. 9,327,166, which is a continuation-in-part of U.S. patent application Ser. No. 13/872,354, filed Apr. 29, 2013, now U.S. Pat. No. 9,302,156, the entire disclosures of which are hereby incorporated herein by reference.

U.S. patent application Ser. No. 14/145,648 is also a continuation-in-part of U.S. patent application Ser. No. 13/913,670, filed Jun. 10, 2013, now U.S. Pat. No. 9,126,083, the entire disclosure of which is hereby incorporated herein by reference.

U.S. patent application Ser. No. 14/145,648 is also a continuation-in-part of U.S. patent application Ser. No. 13/611,376, filed Sep. 12, 2012, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to durable regulation weight golf balls having a diameter of at least 1.70 inches and incorporating a foamed intermediate layer.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into two general classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., single layer core and single layer cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material, and a cover.

Examples of golf ball materials range from rubber materials, such as balata, styrene butadiene, polybutadiene, or polyisoprene, to thermoplastic or thermoset resins such as ionomers, polyolefins, polyamides, polyesters, polyurethanes, polyureas and/or polyurethane/polyurea hybrids, and blends thereof. Typically, outer layers are formed about the spherical outer surface of an innermost golf ball layer via compression molding, casting, or injection molding.

From the perspective of a golf ball manufacturer, it is desirable to have materials exhibiting a wide range of properties, such as compression, coefficient of restitution (CoR), spin, and “feel” because this enables the manufacturer to make and sell golf balls suited to differing levels of ability and/or preferences. A good way to optimize the requirements of good speed, spin, feel, and durability is through a multi-layer construction. Multi-layer balls include a core, a cover layer, and one or more intermediate layers situated between the core and the cover layer.

Golf ball manufacturers have used foamed intermediate layers to soften feel as well as impact other characteristics such as golf ball spin profile. Feel generally refers to the sensation that a player experiences when striking the ball with the club and it is a difficult property to quantify. Most players prefer balls having a soft feel, because the player experience a more natural and comfortable sensation when their club face makes contact with these balls. Balls having a softer feel are particularly desirable when making short shots around the green, because the player senses more with such balls. The feel of the ball primarily depends upon the hardness and compression of the ball. Typically, golf balls having a high compression center will feel harder.

Meanwhile, spin rate refers to the golf ball's rate of rotation after it is struck by a club. Balls having a relatively high spin rate are advantageous for short distance shots made with irons and wedges. Professional and highly skilled amateur golfers can place a back spin more easily on such balls. This helps a player better control the ball and improves shot accuracy and placement. By placing the right amount of spin on the ball, the player can get the ball to stop precisely on the green or place a fade on the ball during approach shots. On the other hand, recreational players who cannot intentionally control the spin of the ball when hitting it with a club are less likely to use high spin balls. For such players, the ball can spin sideways more easily and drift far-off the course, especially if it is hooked or sliced.

Spin rate can be controlled by varying the materials and/or reallocating the density of the various layers of a golf ball. In some instances, the weight from the outer portions of the ball is redistributed toward the center in order to decrease the moment of inertia, thereby increasing the spin rate. In other instances, the weight from the inner portion of the ball is redistributed outward to increase the moment of inertia, thereby decreasing the spin rate.

One example of a golf ball having a foamed intermediate layer is Sullivan, Ladd, and Hebert, U.S. Pat. No. 7,708,654 (“the '654 patent”). The '654 patent discloses a golf ball having a foamed intermediate layer (14) made of a highly neutralized polymer having a reduced specific gravity (less than 0.95) and disposed between a core (12) and a cover (16) (See FIG. 1). According to the '654 Patent, the foamed intermediate layer can be an outer core, a mantle layer, or an inner cover. The reduction in specific gravity of the intermediate layer is caused by foaming the composition of the layer and this reduction can be as high as 30%. The '654 Patent also discloses that foamed compositions such as foamed polyurethanes and polyureas may be used to form the intermediate layer.

Meanwhile, Tutmark, U.S. Pat. No. 8,272,971 is directed to golf balls containing an element that reduces the distance of the ball's flight path. In one embodiment, the ball includes a core, a cover, and a cavity that is formed between core and cover and may be filled by a foamed polyurethane “middle layer” in order to dampen the ball's flight properties. The foam of the middle layer is relatively light in weight; and the core is relatively heavy and dense. According to the '971 Patent, when a golfer strikes the ball with a club, the foam in the middle layer actuates and compresses, thereby absorbing much of the impact from the impact of the ball.

Additionally, Sullivan et al., U.S. Pat. Nos. 6,995,191 and 7,259,191 are directed to golf balls incorporating a foamed intermediate layer of castable reactive liquid polymer formed about a non-foamed core. The non-foamed core has any dimension as long as the overall diameter of the core and foamed intermediate layer combined is in the range of about 1.50 inches to about 1.66 inches. See U.S. Pat. No. 6,995,191 e.g., at col. 2, ll. 58-59 and col. 11, ll. 63-65; and U.S. Pat. No. 7,259,191 at col. 3, ll. 1-2 and col. 12, ll 1-3.

Unfortunately, golf ball manufacturers have encountered durability problems in golf balls incorporating foamed intermediate layers. Such poor durability is due at least in part to difficulties that arise in connection with molding of the foamed intermediate layer about the subassembly/core. The resulting defects may not be visibly apparent on the golf ball surface, but directly impact playability nonetheless.

One such difficulty involves trying to center the core or other subassembly in a castable intermediate layer foam composition deposited within a first mold cavity of a given pair of mold half shells. In this regard, the core/subassembly is typically either placed directly into the foam composition or is held in position such as by an overhanging vacuum or suction apparatus to contact the material in the mold cavity. The core/subassembly generally does not center immovably in the foam composition until a sufficient degree of polymerization and viscosity build occurs in the foam composition before the mold is closed. And even when support devices such as pins are used to support the core/subassembly until sufficient cure occurs to center the core/subassembly, a non-centered core/subassembly can nevertheless result in the finished golf ball respect to that foamed layer and therefore also with respect to outer layers formed about the foamed layer. Meanwhile, there is a known tendency for a foamed layer itself to break or tear apart when forming an outer layer about the foamed intermediate layer.

Accordingly, there still remains a need to develop golf ball constructions that lend themselves to better centering of a core/subassembly in a foamed intermediate layer composition and meanwhile also reduce the aforementioned tendency of the foamed layer to break or tear apart when molding an outer layer thereabout. Such constructions, if also able to produce desirable playing characteristics, would be particularly useful. Golf balls of the invention and methods of making same address and solve these needs.

SUMMARY OF THE INVENTION

Accordingly, golf balls of the invention achieve soft feel and durably incorporate a foamed intermediate layer without sacrificing desired playing characteristics. The constructions of golf balls of the invention facilitate centering of the core/subassembly in the foamed intermediate layer and reduce the aforementioned tendency of the foamed layer to break or tear apart when molding an outer layer thereabout and may be used in connection with thermoset and thermoplastic foam compositions alike.

In one embodiment, the inventive golf ball has a diameter of 1.700 inches or greater, a regulation weight of 1.620 oz. or less, a CoR of at least 0.700, and comprises: a core comprising a rubber composition and having a first specific gravity that is greater than 1.0 g/cc; and an intermediate layer having an outer diameter of about 1.680 inches or greater and consisting of a foamed polyurethane composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising a polyurethane composition and having a third specific gravity that is greater than 1.0 g/cc; and wherein the first specific gravity is less than the third specific gravity. In one such embodiment, the core may have a diameter of 1.580 inches or greater.

In some embodiments, the foamed polyurethane composition of the intermediate layer may be a thermoset material. In other embodiments, the polyurethane composition of the cover layer may be a thermoplastic material.

In one embodiment, the intermediate layer may have an outer surface hardness (H_(inner surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient. In one such embodiment, the core may have an outer surface hardness (R_(inner core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient. In an alternative embodiment, the core may have an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being equal to or less than the H_(core center) to provide a zero to negative hardness gradient.

In a different embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the H_(inner surface of IL) to provide a zero to negative hardness gradient.

In one embodiment, H_(outer surface of IL) may be greater than 50 Shore D. In another embodiment, H_(outer surface of IL) may be 50 Shore D or less.

In a particular embodiment, the third specific gravity may be greater than the first specific gravity. In one such embodiment, the second specific gravity may differ from each of the first specific gravity and the third specific gravity by from about 0.20 g/cc to about 0.30 g/cc.

In some embodiments, the foamed intermediate layer may have an outer diameter of greater than 1.68 inches, or about 1.69 inches or greater.

In another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, a CoR of at least 0.700, and comprises: an inner core layer comprising a rubber composition and having a first specific gravity that is less than 1.0 g/cc; and an outer core layer comprising an unfoamed highly neutralized (HNP) composition and having a second specific gravity of less than 1.2 g/cc; and an intermediate layer having an outer diameter of about 1.680 or greater and consisting of a foamed HNP composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the inner core layer may have a diameter of 0.500 inches or greater, the outer core layer may have an outer diameter of 1.62 inches or less, and the cover layer may have an outer diameter of 1.720 inches or greater.

In one such embodiment, the first specific gravity and third specific gravity may be substantially similar and less than the second specific gravity and fourth specific gravity. In some such embodiments, the second specific gravity and fourth specific gravity may be substantially similar. And the first specific gravity and third specific gravity may meanwhile differ by up to about 0.35 g/cc.

In one embodiment, the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (R_(inner surface of IL)), the H_(outer surface of IL) being greater than the R_(inner surface of IL) to provide a positive hardness gradient. In a particular such embodiment, the outer core layer may have an outer surface hardness (H_(core surface)) and the inner core layer may have a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a negative hardness gradient. In an alternative such embodiment, the outer core layer may have an outer surface hardness (H_(core surface)) and the inner core layer may have a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.

In a different embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the H_(inner surface of IL) to provide a zero to negative hardness gradient.

In one embodiment, H_(outer surface of IL) may be greater than 50 Shore D. In another embodiment, H_(outer surface of IL) may be 50 Shore D or less.

In other embodiments, the intermediate layer may have an outer diameter of greater than 1.68 inches or about 1.69 inches or greater.

In yet another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.750 inches, a CoR of at least 0.700, and comprises: a core comprising a rubber composition and having a first specific gravity of greater than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; and an inner cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the core layer may have a diameter of 1.50 inches or less.

In one embodiment, the first specific gravity may be less than the fourth specific gravity, and the second specific gravity may be less than the third specific gravity.

In a particular such embodiment, the first specific gravity and fourth specific gravity may differ by up to 0.10 and the second specific gravity and the third specific gravity may differ by up to 0.35.

In one embodiment, the intermediate layer may have an outer surface hardness (H_(inner surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the R_(inner surface of IL) to provide a positive hardness gradient.

In one such embodiment, the core may have a surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.

In other embodiments, the intermediate layer may have an outer diameter of greater than 1.68 inches or about 1.69 inches or greater.

In still another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, a CoR of at least 0.700, and comprises: a core comprising an HNP composition and having a first specific gravity that is less than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the core may have a diameter of 1.600 inches or greater; and the cover may have an outer diameter of 1.720 inches or greater.

In one embodiment, the first specific gravity and third specific gravity may be substantially similar and greater than the second specific gravity. In a specific such embodiment, the first specific gravity differs from each of the second specific gravity and the third specific gravity by up to about 0.35 g/cc.

In a particular embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the R_(inner surface of IL) to provide a positive hardness gradient. In one such embodiment, the core may have an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.

In other embodiments, the intermediate layer may have an outer diameter of greater than 1.68 inches or about 1.69 inches or greater.

DETAILED DESCRIPTION OF THE INVENTION

Golf balls of the invention have soft feel and yet durably incorporate a foamed intermediate layer without sacrificing desired playing characteristics. The constructions of golf balls of the invention facilitate centering of the core/subassembly in the foamed intermediate layer and reduce the aforementioned tendency of the foamed layer to break or tear apart when molding an outer layer thereabout and may be used in connection with thermoset and thermoplastic foam compositions alike.

In one embodiment, the inventive golf ball has a diameter of 1.700 inches or greater, a regulation weight of 1.620 oz. or less, a CoR of at least 0.700 and comprises: a core comprising a rubber composition and having a first specific gravity that is greater than 1.0 g/cc; and an intermediate layer having an outer diameter of about 1.680 inches or greater and consisting of a foamed polyurethane composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising a polyurethane composition and having a third specific gravity that is greater than 1.0 g/cc; and wherein the first specific gravity is less than the third specific gravity. In a particular such embodiment, the core may have a diameter of 1.580 inches or greater.

The foamed intermediate layer in alternative embodiments may have an outer diameter of greater than 1.68 inches, or about 1.69 inches or greater, or at least 1.69 inches.

In some embodiments, the foamed polyurethane composition of the intermediate layer may be a thermoset material. In other embodiments, the polyurethane composition of the cover layer may be a thermoplastic material.

In one embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient. In one such embodiment, the core may have an outer surface hardness (H_(inner core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient. In an alternative embodiment, the core may have an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being equal to or less than the H_(core center) to provide a zero to negative hardness gradient.

In a different embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the H_(inner surface of IL) to provide a zero to negative hardness gradient.

In particular embodiments, the positive hardness gradient of the foamed intermediate layer may be at least 2 Shore D units, or at least 3 Shore D units, or at least 5 Shore D units. In different embodiments, the negative hardness gradient of the foamed intermediate layer may be at least 2 Shore D units, or at least 3 Shore D units, or at least 5 Shore D units. Embodiments are indeed envisioned wherein the negative hardness gradient or positive hardness gradient of the foamed intermediate layer may be 10 or greater Shore D hardness points.

In one embodiment, H_(outer surface of IL) may be greater than 50 Shore D. In another embodiment, H_(outer surface of IL) may be 50 Shore D or less.

In a particular embodiment, the third specific gravity may be greater than the first specific gravity. In one such embodiment, the second specific gravity may differ from each of the first specific gravity and the third specific gravity by from about 0.20 g/cc to about 0.30 g/cc.

In some embodiments, the intermediate layer may have an outer diameter that is greater than 1.68 inches. In other embodiments, the intermediate layer may have an outer diameter of 1.69 inches or greater.

In another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, a CoR of at least 0.700, and comprises: an inner core layer comprising a rubber composition and having a first specific gravity that is less than 1.2 g/cc; and an outer core layer comprising an unfoamed highly neutralized (HNP) composition and having a second specific gravity of less than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the inner core layer may have a diameter of 0.500 inches or greater, the outer core layer may have an outer diameter of 1.62 inches or less, and the cover layer may have an outer diameter of 1.720 inches or greater.

In one such embodiment, the first specific gravity and third specific gravity may be substantially similar and less than the second specific gravity and fourth specific gravity. In some such embodiments, the second specific gravity and fourth specific gravity may be substantially similar. And the first specific gravity and third specific gravity may meanwhile differ by up to about 0.35 g/cc.

In one embodiment, the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the R_(inner) surface of IL to provide a positive hardness gradient. In a particular such embodiment, the outer core layer may have an outer surface hardness (H_(core surface)) and the inner core layer may have a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a negative hardness gradient. In an alternative such embodiment, the outer core layer may have an outer surface hardness (H_(core surface)) and the inner core layer may have a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.

In a different embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the R_(inner surface of IL) to provide a zero to negative hardness gradient.

In one embodiment, H_(outer surface of IL) may be greater than 50 Shore D. In another embodiment, H_(outer surface of IL) may be 50 Shore D or less. In particular embodiments, H_(outer surface of IL) may be between 50 shore D and about 75 Shore D, or between 55 shore D and about 75 Shore D, or between 60 shore D and about 75 Shore D, or between 65 shore D and about 75 Shore D, or between 70 shore D and about 75 Shore D. Alternatively, H_(outer surface of IL) may be from about 20 Shore D to 50 shore D, or from about 25 Shore D to 50 shore D, or from about 30 Shore D to 50 shore D, or from about 35 Shore D to 50 shore D, or from about 40 Shore D to 50 shore D, or from about 45 Shore D to 50 shore D.

In some embodiments, the intermediate layer may have an outer diameter that is greater than 1.68 inches. In other embodiments, the intermediate layer may have an outer diameter of 1.69 inches or greater.

In yet another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.750 inches, a CoR of at least 0.700, and comprises: a core comprising a rubber composition and having a first specific gravity of greater than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; and an inner cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the core layer may have a diameter of 1.50 inches or less.

In one embodiment, the first specific gravity may be less than the fourth specific gravity and the second specific gravity may be less than the third specific gravity.

In a particular such embodiment, the first specific gravity and fourth specific gravity may differ by up to 0.10 and the second specific gravity and the third specific gravity may differ by up to 0.35.

In one embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient.

In one such embodiment, the core may have a surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.

In some embodiments, the intermediate layer may have an outer diameter that is greater than 1.68 inches. In other embodiments, the intermediate layer may have an outer diameter of 1.69 inches or greater.

In still another construction, a golf ball of the invention may have a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, a CoR of at least 0.700, and comprises: a core comprising an HNP composition and having a first specific gravity that is less than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc.

In a particular embodiment, the core may have a diameter of 1.600 inches or greater; and the cover may have an outer diameter of 1.720 inches or greater.

In one embodiment, the first specific gravity and third specific gravity may be substantially similar and greater than the second specific gravity. In a specific such embodiment, the first specific gravity differs from each of the second specific gravity and the third specific gravity by up to about 0.35 g/cc.

In a particular embodiment, the intermediate layer may have an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)) the H_(outer surface of IL) being greater than the R_(inner surface of IL) to provide a positive hardness gradient. In one such embodiment, the core may have an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core) surface being greater than the H_(core center) to provide a positive hardness gradient.

In some embodiments, the layers about which the foamed intermediate layer is formed may be referred to collectively as the “subassembly”. In one specific embodiment, the subassembly may have an outer diameter of 1.66 inches or less. In a different embodiment, the subassembly may have an outer diameter of greater than 1.66 inches. In yet another embodiment, the subassembly may have an outer diameter of about 1.66 inches. In still another embodiment, the subassembly may have an outer diameter of 1.66 inches. In each of these embodiments, the foamed intermediate layer may meanwhile have an outer diameter of at least about 1.68 inches, or of at least 1.68 inches, or of greater than about 1.68 inches, or of greater than 1.68 inches, or of about 1.69 inches or greater, or of 1.69 inches or greater. Golf balls having various constructions may be made in accordance with this invention.

For example, the golf ball has at least three layers (is at least three piece) but may alternatively have a four-piece, or five-piece, etc., construction. Meanwhile, the subassembly may constsit of a single spherical center or alternatively be multi-layered, having two or more layers.

The term“layer” as used herein means generally any spherical portion of the golf ball. The diameter and thickness of the different layers along with properties such as hardness and compression may vary depending upon the construction and desired playing performance properties of the golf ball, as long as the golf ball has a regulation weight, an overall diameter of at least 1.70 inches, and a foamed intermediate layer having an outside diameter of at least about 1.68 inches, or of at least 1.68 inches, or of greater than about 1.68 inches, or of greater than 1.68 inches, or of about 1.69 inches or greater, or of 1.69 inches or greater.

In a specific construction of a golf ball of the invention, the outer diameters of the subassembly (rubber core), foamed intermediate layer (foamed polyurethane composition), and cover (unfoamed polyurethane composition) are 1.58 inches, 1.68 inches, and 1.70 inches, respectively. In this embodiment, a ratio of the subassembly outer diameter to the foamed intermediate layer outer diameter is 1.58:1.68 or 0.94:1.0, while a ratio of cover outer diameter to foamed intermediate layer outer diameter is 1.70:1.68 or 1.01:1.0. The foamed intermediate layer, having a thickness of (1.68-1.58)/2 or 0.05 inches, may be durably formed about the 1.58 inch diameter subassembly. Meanwhile, the thickness of the cover provided about the foamed intermediate layer is (1.70-1.68)/2 or 0.01 inches.

In another specific embodiment, the outer diameters of the subassembly (rubber inner core surrounded by HNP outer core layer), foamed intermediate layer (foamed HNP composition), and cover (unfoamed ionomer composition) are 0.500 inches, 1.62 inches, 1.68 inches, and 1.720 inches, respectively, and a ratio of the subassembly outer diameter to foamed intermediate layer outer diameter is 1.62:1.68 or 0.96:1.0, while a ratio of cover outer diameter to foamed intermediate layer outer diameter is 1.720:1.68 or 1.02:1.0. In this embodiment, the foamed intermediate layer, having a thickness of (1.68-1.62)/2 or 0.03 inches, may be durably formed about the 1.62 inch diameter subassembly. Meanwhile, the thickness of the cover provided about the foamed intermediate layer is (1.720-1.68)/2 or 0.04 inches.

In yet another specific embodiment, the outer diameters of the subassembly (rubber center), the foamed intermediate layer (foamed HNP composition), the inner cover (unfoamed ionomer composition) and the outer cover (unfoamed polyurethane composition) are 1.500 inches, 1.68 inches, 1.72 inches, and 1.750 inches, respectively, and a ratio of the subassembly outer diameter to foamed intermediate layer outer diameter is 1.500:1.68 or 0.89:1.0, while a ratio of inner cover outer diameter to foamed intermediate layer outer diameter is 1.720:1.68 or 1.02:1.0, and a ratio of outer cover outer diameter to foamed intermediate layer outer diameter is 1.750:1.68 or 1.04:1.0. In this embodiment, the foamed intermediate layer, having a thickness of (1.68-1.500)/2 or 0.09 inches, may be durably formed about the 1.62 inch diameter subassembly. Meanwhile, the thickness of the cover provided about the foamed intermediate layer is (1.720-1.68)/2 or 0.04 inches.

In still another specific embodiment, the outer diameters of the subassembly (spherical HNP core), the foamed intermediate layer (foamed HNP composition), and the cover (unfoamed ionomer composition) are 1.62 inches, 1.68 inches, and 1.720 inches, respectively, and a ratio of the subassembly outer diameter to foamed intermediate layer outer diameter is 1.62:1.68 or 0.96:1.0, while a ratio of cover outer diameter to foamed intermediate layer outer diameter is 1.720:1.68 or 1.02:1.0. In this embodiment, the foamed intermediate layer, having a thickness of (1.68-1.62)/2 or 0.03 inches, may be durably formed about the 1.62 inch diameter subassembly. Meanwhile, the thickness of the cover provided about the foamed intermediate layer is (1.720-1.68)/2 or 0.04 inches.

The overall diameter of the subassembly may be within a range having a lower limit of 0.500 or 1.000 or 1.300 or 1.400 or 1.500 or 1.580 or 1.600 or 1.610 or 1.620 inches and an upper limit of 1.600 or 1.610 or 1.620 or 1.630 or 1.640 or 1.650 or 1.660 or greater than 1.660 inches, wherein the upper limit is greater than the lower limit (e.g., when the lower limit is 1.610 inches, the upper limit is 1.620, 1.630, 1.640, 1.650, 1.660 or greater than 1.660 inches).

In particular embodiments, the subassembly may be a single or multi-layer core having an overall diameter of 1.450 inches or 1.500 inches or 1.510 inches or 1.530 inches or 1.550 inches or 1.570 inches or 1.580 inches or 1.590 inches or 1.600 inches or 1.610 inches or 1.620 or 1.640 or 1.66 or greater than 1.66 inches.

Meanwhile, the subassembly is always adjacent to and formed within an inner surface of the foamed intermediate layer.

Foamed Intermediate Layer Composition

In general, foam compositions are made by forming gas bubbles in a polymer mixture using a foaming (blowing) agent. As the bubbles form, the mixture expands and forms a foam composition that can be molded into an end-use product having either an open or closed cellular structure. Flexible foams generally have an open cell structure, where the cells walls are incomplete and contain small holes through which liquid and air can permeate. Such flexible foams are used for automobile seats, cushioning, mattresses, and the like. Rigid foams generally have a closed cell structure, where the cell walls are continuous and complete, and are used for used for automobile panels and parts, building insulation and the like.

In the present invention, the foamed intermediate layer comprises a lightweight foam thermoplastic or thermoset polymer composition that may range from relatively rigid foam to very flexible foam. A wide variety of thermoplastic and thermoset materials may be used in forming the foam composition of this invention including, for example, polyurethanes; polyureas; copolymers, blends and hybrids of polyurethane and polyurea; olefin-based copolymer ionomer resins (for example, Surlyn® ionomer resins and DuPont HPF® 1000 and HPF® 2000, commercially available from DuPont; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® 10 ionomers of ethylene acrylic acid copolymers, commercially available from Dow Chemical Company; and Clarix® ionomer resins, commercially available from A. Schulman Inc.); polyethylene, including, for example, low density polyethylene, linear low density polyethylene, and high density polyethylene; polypropylene; rubber-toughened olefin polymers; acid copolymers, for example, poly(meth)acrylic acid, which do not become part of an ionomeric copolymer; plastomers; flexomers; styrene/butadiene/styrene block copolymers; styrene/ethylene-butylene/styrene block copolymers; dynamically vulcanized elastomers; copolymers of ethylene and vinyl acetates; copolymers of ethylene and methyl acrylates; polyvinyl chloride resins; polyamides, poly(amide-ester) elastomers, and graft copolymers of ionomer and polyamide including, for example, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc; cross-linked trans-polyisoprene and blends thereof; polyester-based thermoplastic elastomers, such as Hytrel®, commercially available from DuPont or RiteFlex®, commercially available from Ticona Engineering Polymers; polyurethane-based thermoplastic elastomers, such as Elastollan®, commercially available from BASF; synthetic or natural vulcanized rubber; and combinations thereof.

Castable polyurethanes, polyureas, and hybrids of polyurethanes-polyureas are particularly desirable for forming the foamed intermediate layer because these materials can be used to make a golf ball having good playing performance properties as discussed further below. By the term, “hybrids of polyurethane and polyurea,” it is meant to include copolymers and blends thereof.

Basically, polyurethane compositions contain urethane linkages formed by the reaction of a multi-functional isocyanate containing two or more NCO groups with a polyol having two or more hydroxyl groups (OH—OH) sometimes in the presence of a catalyst and other additives. Generally, polyurethanes can be produced in a single-step reaction (one-shot) or in a two-step reaction via a prepolymer or quasi-prepolymer. In the one-shot method, all of the components are combined at once, that is, all of the raw ingredients are added to a reaction vessel, and the reaction is allowed to take place. In the prepolymer method, an excess of polyisocyanate is first reacted with some amount of a polyol to form the prepolymer which contains reactive NCO groups. This prepolymer is then reacted again with a chain extender or curing agent polyol to form the final polyurethane. Polyurea compositions, which are distinct from the above-described polyurethanes, also can be formed. In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group (—N═C═O) with an amine group (NH or NH₂). Polyureas can be produced in similar fashion to polyurethanes by either a one shot or prepolymer method. In forming a polyurea polymer, the polyol would be substituted with a suitable polyamine. Hybrid compositions containing urethane and urea linkages also may be produced. For example, when polyurethane prepolymer is reacted with amine-terminated curing agents during the chain-extending step, any excess isocyanate groups in the prepolymer will react with the amine groups in the curing agent. The resulting polyurethane-urea composition contains urethane and urea linkages and may be referred to as a hybrid. In another example, a hybrid composition may be produced when a polyurea prepolymer is reacted with a hydroxyl-terminated curing agent. A wide variety of isocyanates, polyols, polyamines, and curing agents can be used to form the polyurethane and polyurea compositions as discussed further below.

Foam intermediate layers are often cast about inner layers. Casting is a common method of producing a foamed urethane, urea or urethane/urea hybrid outer layer about a core or other subassembly. A desired benefit of casting golf ball layers about subassemblies is that the resulting layer has a substantially uniform thickness.

In a casting process, a castable composition is introduced into a first mold cavity of a given pair of mold half shells. The core/subassembly is then either placed directly into the composition or is held in position (e.g., by an overhanging vacuum or suction apparatus) to contact the material in what will be the spherical center of the mold cavity pair. Once the castable composition is at least partially cured (e.g., to a point where the core will not substantially move), additional castable composition is introduced into a second mold cavity of each pair, and the mold is closed. The closed mold is then subjected to heat and pressure to cure the composition, thereby forming the outer layer about the core. The mold cavities can have smooth surfaces or include a negative dimple pattern to impart dimples in the composition during the molding process where the cast layer is a cover, for example.

It is important that a core/subassembly be centered in the castable composition within a mold cavity before the mold halves are mated because a non-centered core/subassembly can create and result in undesirable playing characteristics. As a result, support devices such as pins are commonly used to support the core/subassembly until sufficient cure of the castable composition occurs to center the core/subassembly.

Thus, it is important to coordinate the foam composition's rise time (the time from dispensing the foam composition into a mold until the foam composition reaches its maximum height or thickness) and sufficient cure and viscosity build for centering so that the core/subassembly does not continue to move while the foam composition rises, so that the core/subassembly is centered in finished golf ball with respect to that foamed layer as well as outer layers formed about the foamed layer.

Securing means (such as pins) are typically provided in the molding equipment in order to hold the core/subassembly in a centered position while the conventional compositions develop sufficient viscosity or degree of cure within the mold to center the core/subassembly immovably. Such pin molds generally contain a series of protruding pins designed to secure the core/subassembly concentrically in place within in the layer composition prior to sufficient cure. A predetermined shot weight is dispensed into a pin mold, the core/subassembly is immediately plunged, and the two mold halves are mated. The pins are designed to hold the core/assembly in the correct position while the composition cures to completion, thereby producing a concentrically placed golf ball core/subassembly surrounded by an outer layer.

The constructions of golf balls of the invention better center a core or other subassembly within foamed intermediate layer material so that in the resulting golf ball, the subassembly is properly centered in relation to the foamed intermediate layer as well as with respect to layers formed about the foamed intermediate layer. And simultaneously, outer layers may be durably formed about the foamed intermediate layer with significant reduction of heretofore known instances of blowout of the foamed intermediate layer when molding outer layers thereabout.

Meanwhile, a highly neutralized composition (HNP) may be incorporated in a golf ball of the invention, comprising an acid copolymer, a non-acid polymer, an organic acid or salt thereof, and a cation source optionally has one or more of the following properties:

-   -   (a) the acid copolymer does not include a softening monomer;     -   (b) the acid of the acid copolymer is selected from acrylic acid         and methacrylic acid;     -   (c) the acid of the acid copolymer is present in the acid         copolymer in an amount of from 15 mol % to 30 mol %, based on         the total weight of the acid copolymer;     -   (d) the non-acid polymer is an alkyl acrylate rubber selected         from ethylene-alkyl acrylates and ethylene-alkyl methacrylates;     -   (e) the non-acid polymer is present in an amount of greater than         50 wt %, based on the combined weight of the acid copolymer and         the non-acid polymer;     -   (f) the non-acid polymer is present in an amount of 20 wt % or         greater, based on the total weight of the highly neutralized         composition;     -   (g) the non-acid polymer is present in an amount of less than 50         wt %, based on the combined weight of the acid copolymer and the         non-acid polymer;     -   (h) the highly neutralized polymer composition has a solid         sphere compression of 40 or less and a coefficient of         restitution of 0.820 or greater;     -   (i) the highly neutralized polymer composition has a solid         sphere compression of 100 or greater and a coefficient of         restitution of 0.860 or greater;     -   (j) the organic acid salt is a metal salt of oleic acid;     -   (k) the organic salt is magnesium oleate;     -   (l) the organic salt is present in an amount of 30 parts or         greater, per 100 parts of acid copolymer and non-acid copolymer         combined; and     -   (m) the cation source is present in an amount sufficient to         neutralize 110% or greater of all acid groups present in the         composition.

To prepare the foamed polyurethane, polyurea, or other polymer composition, a foaming agent is introduced into the polymer formulation. In general, there are two types of foaming agents: physical foaming agents and chemical foaming agents.

Physical Foaming Agents.

These foaming agents typically are gasses that are introduced under high pressure directly into the polymer composition. Chlorofluorocarbons (CFCs) and partially halogenated chlorofluorocarbons are effective, but these compounds are banned in many countries because of their environmental side effects. Alternatively, aliphatic and cyclic hydrocarbon gasses such as isobutene and pentane may be used. Inert gasses, such as carbon dioxide and nitrogen, also are suitable.

Chemical Foaming Agents.

These foaming agents typically are in the form of powder, pellets, or liquids and they are added to the composition, where they decompose or react during heating and generate gaseous by-products (for example, nitrogen or carbon dioxide). The gas is dispersed and trapped throughout the composition and foams it.

Preferably, a chemical foaming agent is used to prepare the foam compositions of this invention. Chemical blowing agents may be inorganic, such as ammonium carbonate and carbonates of alkalai metals, or may be organic, such as azo and diazo compounds, such as nitrogen-based azo compounds. Suitable azo compounds include, but are not limited to, 2,2′-azobis(2-cyanobutane), 2,2′-azobis(methylbutyronitrile), azodicarbonamide, p,p′-oxybis(benzene sulfonyl hydrazide), p-toluene sulfonyl semicarbazide, p-toluene sulfonyl hydrazide. Other foaming agents include any of the Celogens® sold by Crompton Chemical Corporation, and nitroso compounds, sulfonylhydrazides, azides of organic acids and their analogs, triazines, tri- and tetrazole derivatives, sulfonyl semicarbazides, urea derivatives, guanidine derivatives, and esters such as alkoxyboroxines. Also, foaming agents that liberate gasses as a result of chemical interaction between components such as mixtures of acids and metals, mixtures of organic acids and inorganic carbonates, mixtures of nitriles and ammonium salts, and the hydrolytic decomposition of urea may be used. Water is a preferred foaming agent. When added to the polyurethane formulation, water will react with the isocyanate groups and form carbamic acid intermediates. The carbamic acids readily decarboxylate to form an amine and carbon dioxide. The newly formed amine can then further react with other isocyanate groups to form urea linkages and the carbon dioxide forms the bubbles to produce the foam.

During the decomposition reaction of certain chemical foaming agents, more heat and energy is released than is needed for the reaction. Once the decomposition has started, it continues for a relatively long time period. If these foaming agents are used, longer cooling periods are generally required. Hydrazide and azo-based compounds often are used as exothermic foaming agents. On the other hand, endothermic foaming agents need energy for decomposition. Thus, the release of the gasses quickly stops after the supply of heat to the composition has been terminated. If the composition is produced using these foaming agents, shorter cooling periods are needed. Bicarbonate and citric acid-based foaming agents can be used as exothermic foaming agents.

Other suitable foaming agents include expandable gas-containing microspheres. Exemplary microspheres consist of an acrylonitrile polymer shell encapsulating a volatile gas, such as isopentane gas. This gas is contained within the sphere as a blowing agent. In their unexpanded state, the diameter of these hollow spheres range from 10 to 17 μm and have a true density of 1000 to 1300 kg/m³. When heated, the gas inside the shell increases its pressure and the thermoplastic shell softens, resulting in a dramatic increase of the volume of the microspheres. Fully expanded, the volume of the microspheres will increase more than 40 times (typical diameter values would be an increase from 10 to 40 μm), resulting in a true density below 30 kg/m³ (0.25 lbs/gallon). Typical expansion temperatures range from 80-190° C. (176-374° F.). Such expandable microspheres are commercially available as Expancel® from Expancel of Sweden or Akzo Nobel.

As an alternative to chemical and physical foaming agents or in addition to such foaming agents, as described above, other types of fillers that lower the specific gravity of the composition can be used in accordance with this invention. For example, polymeric, ceramic, and glass unfilled microspheres having a density of 0.1 to 1.0 g/cc and an average particle size of 10 to 250 microns can be used to help lower specific gravity of the composition and achieve the desired density and physical properties.

Additionally, BASF polyurethane materials sold under the trade name Cellasto® and Elastocell®, microcellular polyurethanes, Elastopor® H that is a closed-cell polyurethane rigid foam, Elastoflex® W flexible foam systems, Elastoflex® E semiflexible foam systems, Elastofoam® flexible integrally-skinning systems, Elastolit® D/K/R integral rigid foams, Elastopan® S, Elastollan® thermoplastic polyurethane elastomers (TPUs), and the like may be used in accordance with the present invention. Bayer also produces a variety of materials sold as Texin® TPUs, Baytec® and Vulkollan® elastomers, Baymer® rigid foams, Baydur® integral skinning foams, Bayfit® flexible foams available as castable, RIM grades, sprayable, and the like that may be used. Additional foam materials that may be used herein include polyisocyanurate foams and a variety of “thermoplastic” foams, which may be cross-linked to varying extents using free-radical (for example, peroxide) or radiation cross-linking (for example, UV, IR, Gamma, EB irradiation). Also, foams may be prepared from polybutadiene, polystyrene, polyolefin (including metallocene and other single site catalyzed polymers), ethylene vinyl acetate (EVA), acrylate copolymers, such as EMA, EBA, Nucrel®-type acid co and terpolymers, ethylene propylene rubber (such as EPR, EPDM, and any ethylene copolymers), styrene-butadiene, and SEBS (any Kraton-type), PVC, PVDC, CPE (chlorinated polyethylene). Epoxy foams, urea-formaldehyde foams, latex foams and sponge, silicone foams, fluoropolymer foams and syntactic foams (hollow sphere filled) also may be used.

In addition to the polymer and foaming agent, the foam composition also may include other ingredients such as, for example, cross-linking agents, chain extenders, surfactants, dyes and pigments, coloring agents, fluorescent agents, adsorbents, stabilizers, softening agents, impact modifiers, antioxidants, antiozonants, and the like. The formulations used to prepare the polyurethane foam compositions of this invention preferably contain a polyol, polyisocyanate, water, an amine or hydroxyl curing agent, surfactant, and a catalyst as described further below.

In one preferred version, the foam composition includes nanoclay particles, more preferably quaternary ammonium nanoclay particulate. While not wishing to be bound by any theory, it is believed that adding the nanoclay to the foam composition helps improve the foam cell structure and morphology. As the nanoclay is dispersed in the foam composition, it helps create a greater number of smaller sized foam cells. Thus, the foam cells are packed together more tightly and cell density is increased. The dimensions and geometry of the foam cells across the matrix tends to be more uniform. The cell structure is maintained as the nanoclay help prevent air from diffusing through the cell walls. The resulting foam material has greater compression strength and modulus. Preferably, the foam composition contains about 0.25 to about 2% and more preferably about 0.25 to about 0.75% of nanoclay particles based on total weight of the composition. Since the addition of the nanoclay may have a catalytic effect on the reaction rate of the reactants used to make the polyurethane foam, it is preferred that the nanoclay be added during the curing step.

Properties of Polyurethane Foams

The polyurethane foam compositions of this invention have numerous chemical and physical properties making them suitable for foamed intermediate layers in golf balls. For example, there are properties relating to the reaction of the isocyanate and polyol components and blowing agent, particularly “cream time,” “gel time,” “rise time,” “tack-free time,” and “free-rise density.” In general, cream time refers to the time period from the point of mixing the raw ingredients together to the point where the mixture turns cloudy in appearance or changes color and begins to rise from its initial stable state. Normally, the cream time of the foam compositions of this invention is within the range of about 20 to about 240 seconds. In general, gel time refers to the time period from the point of mixing the raw ingredients together to the point where the expanded foam starts polymerizing/gelling. Rise time generally refers to the time period from the point of mixing the raw ingredients together to the point where the reacted foam has reached its largest volume or maximum height. The rise time of the foam compositions of this invention typically is in the range of about 60 to about 360 seconds. Tack-free time generally refers to the time it takes for the reacted foam to lose its tackiness, and the foam compositions of this invention normally have a tack-free time of about 60 to about 3600 seconds. Free-rise density refers to the density of the resulting foam when it is allowed to rise unrestricted without a cover or top being placed on the mold.

The density of the foam is an important property and is defines as the weight per unit volume (typically, g/cm³) and can be measured per ASTM D-1622. The hardness, stiffness, and load-bearing capacity of the foam are independent of the foam's density, although foams having a high density typically have high hardness and stiffness. Normally, foams having higher densities have higher compression strength. Surprisingly, the foam compositions used to produce the intermediate layer of the golf balls per this invention have a relatively low density; however, the foams are not necessarily soft and flexible, rather, they may be relatively firm, rigid, or semi-rigid depending upon the desired golf ball properties. Tensile strength, tear-resistance, and elongation generally refer to the foam's ability to resist breaking or tearing, and these properties can be measured per ASTM D-1623. The durability of foams is important, because introducing fillers and other additives into the foam composition can increase the tendency of the foam to break or tear apart. In general, the tensile strength of the foam compositions of this invention is in the range of about 20 to about 1000 psi (parallel to the foam rise) and about 50 to about 1000 psi (perpendicular to the foam rise) as measured per ASTM D-1623 at 23° C. and 50% relative humidity (RH). Meanwhile, the flex modulus of the foams of this invention is generally in the range of about 5 to about 45 kPa as measured per ASTM D-790, and the foams generally have a compressive modulus of 200 to 50,000 psi.

In another test, compression strength is measured on an Instron machine according to ASTM D-1621. The foam is cut into blocks and the compression strength is measured as the force required to compress the block by 10%. In general, the compressive strength of the foam compositions of this invention is in the range of about 100 to about 1800 psi (parallel and perpendicular to the foam rise) as measured per ASTM D-1621 at 23° C. and 50% relative humidity (RH). The test is conducted perpendicular to the rise of the foam or parallel to the rise of the foam. The Percentage (%) of Compression Set also can be used. This is a measure of the permanent deformation of a foam sample after it has been compressed between two metal plates under controlled time and temperature condition (standard—22 hours at 70° C. (158° F.)). The foam is compressed to a thickness given as a percentage of its original thickness that remained “set.” Preferably, the Compression Set of the foam is less than ten percent (10%), that is, the foam recovers to a point of 90% or greater of its original thickness.

Methods of Preparing the Foam Composition

The foam compositions of this invention may be prepared using different methods. In one preferred embodiment, the method involves preparing a castable composition comprising a reactive mixture of a polyisocyanate, polyol, water, curing agent, surfactant, and catalyst. A motorized mixer can be used to mix the starting ingredients together and form a reactive liquid mixture. Alternatively, the ingredients can be manually mixed together. An exothermic reaction occurs when the ingredients are mixed together and this continues as the reactive mixture is dispensed into the mold cavities (otherwise referred to as half-molds or mold cups). The mold cavities may be referred to as first and second, or upper and lower, mold cavities. The mold cavities preferably are made of metal such as, for example, brass or silicon bronze.

Polyisocyanates and Polyols for Making the Polyurethane Foams

As discussed above, a foamed polyurethane composition is used to form the intermediate layer. In general, the polyurethane compositions contain urethane linkages formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). The polyurethanes are produced by the reaction of multi-functional isocyanates containing two or more isocyanate groups with a polyol having two or more hydroxyl groups. The formulation may also contain a catalyst, surfactant, and other additives.

In particular, the foam intermediate layer of this invention may be prepared from a composition comprising an aromatic polyurethane, which is preferably formed by reacting an aromatic diisocyanate with a polyol. Suitable aromatic diisocyanates that may be used in accordance with this invention include, for example, toluene 2,4-diisocyanate (TDI), toluene 2,6-diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI), 2,4′-methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (PMDI), p-phenylene diisocyanate (PPDI), m-phenylene diisocyanate (PDI), naphthalene 1,5-diisocyanate (NDI), naphthalene 2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and homopolymers and copolymers and blends thereof. The aromatic isocyanates are able to react with the hydroxyl or amine compounds and form a durable and tough polymer having a high melting point. The resulting polyurethane generally has good mechanical strength and tear-resistance.

Alternatively, the foamed composition of the intermediate layer may be prepared from a composition comprising aliphatic polyurethane, which is preferably formed by reacting an aliphatic diisocyanate with a polyol. Suitable aliphatic diisocyanates that may be used in accordance with this invention include, for example, isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (“H₁₂ MDI”), meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexane diisocyanate (CHDI), 1,3-bis(isocyanatomethyl)cyclohexane; 1,4-bis(isocyanatomethyl)cyclohexane; and homopolymers and copolymers and blends thereof. The resulting polyurethane generally has good light and thermal stability. Preferred polyfunctional isocyanates include 4,4′-methylene diphenyl diisocyanate (MDI), 2,4′-methylene diphenyl diisocyanate (MDI), and polymeric MDI having a functionality in the range of 2.0 to 3.5 and more preferably 2.2 to 2.5.

Any suitable polyol may be used to react with the polyisocyanate in accordance with this invention. Exemplary polyols include, but are not limited to, polyether polyols, hydroxy-terminated polybutadiene (including partially/fully hydrogenated derivatives), polyester polyols, polycaprolactone polyols, and polycarbonate polyols. In one preferred embodiment, the polyol includes polyether polyol. Examples include, but are not limited to, polytetramethylene ether glycol (PTMEG), polyethylene propylene glycol, polyoxypropylene glycol, and mixtures thereof. The hydrocarbon chain can have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups. Preferably, the polyol of the present invention includes PTMEG.

As discussed further below, chain extenders (curing agents) are added to the mixture to build-up the molecular weight of the polyurethane polymer. In general, hydroxyl-terminated curing agents, amine-terminated curing agents, and mixtures thereof are used.

A catalyst may be employed to promote the reaction between the isocyanate and polyol compounds. Suitable catalysts include, but are not limited to, bismuth catalyst; zinc octoate; tin catalysts such as bis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin (II) chloride, tin (IV) chloride, bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts such as triethylenediamine, triethylamine, tributylamine, 1,4-diaza(2,2,2)bicyclooctane, tetramethylbutane diamine, bis[2-dimethylaminoethyl]ether, N,N-dimethylaminopropylamine, N,N-dimethylcyclohexylamine, N,N,N′,N′,N″-pentamethyldiethylenetriamine, diethanolamine, dimethtlethanolamine, N-[2-(dimethylamino)ethyl]-N-methylethanolamine, N-ethylmorpholine, 3-dimethylamino-N,N-dimethylpropionamide, and N,N′,N″-dimethylaminopropylhexahydrotriazine; organic acids such as oleic acid and acetic acid; delayed catalysts; and mixtures thereof. Zirconium-based catalysts such as, for example, bis(2-dimethyl aminoethyl) ether; mixtures of zinc complexes and amine compounds such as KKAT™ XK 614, available from King Industries; and amine catalysts such as Niax™ A-2 and A-33, available from Momentive Specialty Chemicals, Inc. are particularly preferred. The catalyst is preferably added in an amount sufficient to catalyze the reaction of the components in the reactive mixture. In one embodiment, the catalyst is present in an amount from about 0.001 percent to about 1 percent, and preferably 0.1 to 0.5 percent, by weight of the composition.

In one preferred embodiment, as described above, water is used as the foaming agent—the water reacts with the polyisocyanate compound(s) and forms carbon dioxide gas which induces foaming of the mixture. The reaction rate of the water and polyisocyanate compounds affects how quickly the foam is formed as measured per reaction profile properties such as cream time, gel time, and rise time of the foam.

The hydroxyl chain-extending (curing) agents are preferably selected from the group consisting of ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; monoethanolamine; diethanolamine; triethanolamine; monoisopropanolamine; diisopropanolamine; dipropylene glycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; trimethylolpropane; cyclohexyldimethylol; triisopropanolamine; N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycol bis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol; 1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol; 1,3-bis-[2-(2-hydroxyethoxy) ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}cyclohexane; trimethylolpropane; polytetramethylene ether glycol (PTMEG), preferably having a molecular weight from about 250 to about 3900; and mixtures thereof. Di, tri, and tetra-functional polycaprolactone diols such as, 2-oxepanone polymer initiated with 1,4-butanediol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, or 2,2-bis(hydroxymethyl)-1,3-propanediolsuch, may be used.

Suitable amine chain-extending (curing) agents that can be used in chain-extending the polyurethane prepolymer include, but are not limited to, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-dianiline or “MDA”), m-phenylenediamine, p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-) toluenediamine or “DETDA”, 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane, 3,3′-diethyl-5,5′-dimethyl4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)), 3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-chloroaniline) or “MOCA”), 3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaniline), 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”), 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”), 3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane, 3,3′-dichloro-4,4′-diamino-diphenylmethane, 4,4′-methylene-bis(2,3-dichloroaniline) (i.e., 2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”), 4,4′-bis(sec-butylamino)-diphenylmethane, N,N′-dialkylamino-diphenylmethane, trimethyleneglycol-di(p-aminobenzoate), polyethyleneglycol-di(p-aminobenzoate), polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such as ethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine), imido-bis(propylamine), methylimino-bis(propylamine) (i.e., N-(3-aminopropyl)-N-methyl-1,3-propanediamine), 1,4-bis(3-aminopropoxy)butane (i.e., 3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine), diethyleneglycol-bis(propylamine) (i.e., diethyleneglycol-di(aminopropyl)ether), 4,7,10-trioxatridecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene) diamines, 1,3- or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or 1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophorone diamine, 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines, 3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane, polyoxypropylene diamines, 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane, polytetramethylene ether diamines, 3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaminocyclohexane)), 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane, (ethylene oxide)-capped polyoxypropylene ether diamines, 2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane, 4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such as diethylene triamine, dipropylene triamine, (propylene oxide)-based triamines (i.e., polyoxypropylene triamines), N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine), glycerin-based triamines, (all saturated); tetramines such as N,N′-bis(3-aminopropyl)ethylene diamine (i.e., N₄-amine) (both saturated), triethylene tetramine; and other polyamines such as tetraethylene pentamine (also saturated). One suitable amine-terminated chain-extending agent is Ethacure 300™ (dimethylthiotoluenediamine or a mixture of 2,6-diamino-3,5-dimethylthiotoluene and 2,4-diamino-3,5-dimethylthiotoluene.) The amine curing agents used as chain extenders normally have a cyclic structure and a low molecular weight (250 or less).

When a hydroxyl-terminated curing agent is used, the resulting polyurethane composition contains urethane linkages. On the other hand, when an amine-terminated curing agent is used, any excess isocyanate groups will react with the amine groups in the curing agent. The resulting polyurethane composition contains urethane and urea linkages and may be referred to as a polyurethane/urea hybrid.

Suitable thermoset rubber materials for forming layers include, but are not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”) rubber, styrene-butadiene rubber, styrenic block copolymer rubbers (such as “SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), polyalkenamers such as, for example, polyoctenamer, butyl rubber, halobutyl rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers and plastomers, copolymers of isobutylene and p-alkylstyrene, halogenated copolymers of isobutylene and p-alkylstyrene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and blends of two or more thereof.

The thermoset rubber composition may be cured using conventional curing processes. Suitable curing processes include, for example, peroxide-curing, sulfur-curing, high-energy radiation, and combinations thereof. Preferably, the rubber composition contains a free-radical initiator selected from organic peroxides, high energy radiation sources capable of generating free-radicals, and combinations thereof. In one preferred version, the rubber composition is peroxide-cured. Suitable organic peroxides include, but are not limited to, dicumyl peroxide; n-butyl-4,4-di(t-butylperoxy) valerate; 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane; 2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide; di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3; di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoyl peroxide; t-butyl hydroperoxide; and combinations thereof. In a particular embodiment, the free radical initiator is dicumyl peroxide, including, but not limited to Perkadox® BC, commercially available from Akzo Nobel. Peroxide free-radical initiators are generally present in the rubber composition in an amount of at least 0.05 parts by weight per 100 parts of the total rubber, or an amount within the range having a lower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5 parts or 2.5 parts or 5 parts by weight per 100 parts of the total rubbers, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6 parts or 10 parts or 15 parts by weight per 100 parts of the total rubber. Concentrations are in parts per hundred (phr) unless otherwise indicated. As used herein, the term, “parts per hundred,” also known as “phr” or “pph” is defined as the number of parts by weight of a particular component present in a mixture, relative to 100 parts by weight of the polymer component. Mathematically, this can be expressed as the weight of an ingredient divided by the total weight of the polymer, multiplied by a factor of 100.

The rubber compositions may further include a reactive cross-linking co-agent. Suitable co-agents include, but are not limited to, metal salts of unsaturated carboxylic acids having from 3 to 8 carbon atoms; unsaturated vinyl compounds and polyfunctional monomers (e.g., trimethylolpropane trimethacrylate); phenylene bismaleimide; and combinations thereof. Particular examples of suitable metal salts include, but are not limited to, one or more metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates, wherein the metal is selected from magnesium, calcium, zinc, aluminum, lithium, and nickel. In a particular embodiment, the co-agent is selected from zinc salts of acrylates, diacrylates, methacrylates, and dimethacrylates. In another particular embodiment, the agent is zinc diacrylate (ZDA). When the co-agent is zinc diacrylate and/or zinc dimethacrylate, the co-agent is typically included in the rubber composition in an amount within the range having a lower limit of 1 or 5 or 10 or 15 or 19 or 20 parts by weight per 100 parts of the total rubber, and an upper limit of 24 or 25 or 30 or 35 or 40 or 45 or 50 or 60 parts by weight per 100 parts of the base rubber.

Radical scavengers such as a halogenated organosulfur, organic disulfide, or inorganic disulfide compounds may be added to the rubber composition. These compounds also may function as “soft and fast agents.” As used herein, “soft and fast agent” means any compound or a blend thereof that is capable of making a layer: 1) softer (having a lower compression) at a constant “coefficient of restitution” (COR); and/or 2) faster (having a higher COR at equal compression), when compared to a layer equivalently prepared without a soft and fast agent. Preferred halogenated organosulfur compounds include, but are not limited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zinc pentachlorothiophenol (ZnPCTP). Using PCTP and ZnPCTP in golf ball layers helps produce softer and faster layers. The PCTP and ZnPCTP compounds help increase the resiliency and the coefficient of restitution of the layer. In a particular embodiment, the soft and fast agent is selected from ZnPCTP, PCTP, ditolyl disulfide, diphenyl disulfide, dixylyl disulfide, 2-nitroresorcinol, and combinations thereof.

The rubber composition also may include filler(s) such as materials selected from carbon black, nanoclays (e.g., Cloisite® and Nanofil® nanoclays, commercially available from Southern Clay Products, Inc., and Nanomax® and Nanomer® nanoclays, commercially available from Nanocor, Inc.), talc (e.g., Luzenac HAR® high aspect ratio talcs, commercially available from Luzenac America, Inc.), glass (e.g., glass flake, milled glass, and microglass), mica and mica-based pigments (e.g., Iriodin® pearl luster pigments, commercially available from The Merck Group), and combinations thereof. Metal fillers such as, for example, particulate; powders; flakes; and fibers of copper, steel, brass, tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, and platinum, and alloys and combinations thereof also may be added to the rubber composition to adjust the specific gravity of the composition as needed.

In addition, the rubber compositions may include antioxidants to prevent the breakdown of the elastomers. Also, processing aids such as high molecular weight organic acids and salts thereof may be added to the composition. Suitable organic acids are aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated monofunctional organic acids, multi-unsaturated mono-functional organic acids, and dimerized derivatives thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, and dimerized derivatives thereof. The organic acids are aliphatic, mono-functional (saturated, unsaturated, or multi-unsaturated) organic acids. Salts of these organic acids may also be employed. The salts of organic acids include the salts of barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, or calcium, salts of fatty acids, particularly stearic, behenic, erucic, oleic, linoelic or dimerized derivatives thereof. It is preferred that the organic acids and salts of the present invention be relatively non-migratory (they do not bloom to the surface of the polymer under ambient temperatures) and non-volatile (they do not volatilize at temperatures required for melt-blending.) Other ingredients such as accelerators (for example, tetra methylthiuram), processing aids, dyes and pigments, wetting agents, surfactants, plasticizers, coloring agents, fluorescent agents, chemical blowing and foaming agents, defoaming agents, stabilizers, softening agents, impact modifiers, antiozonants, as well as other additives known in the art may be added to the rubber composition.

Examples of commercially-available polybutadiene rubbers that can be used in accordance with this invention, include, but are not limited to, BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand; SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland, Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Inc of Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber (JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29 MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221, available from Lanxess Corp. of Pittsburgh. Pa.; BR1208, available from LG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L, BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. of Tokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, and EUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE 50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY) Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR 710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co., Ltd. Of Seoul, South Korea; DIENE 55NF, 70AC, and 320 AC, available from Firestone Polymers of Akron, Ohio; and PBR-Nd Group II and Group III, available from Nizhnekamskneftekhim, Inc. of Nizhnekamsk, Tartarstan Republic.

The polybutadiene rubber is used in an amount of at least about 5% by weight based on total weight of composition and is generally present in an amount of about 5% to about 100%, or an amount within a range having a lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upper limit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, the concentration of polybutadiene rubber is about 40 to about 95 weight percent. If desirable, lesser amounts of other thermoset materials may be incorporated into the base rubber. Such materials include the rubbers discussed above, for example, cis-polyisoprene, trans-polyisoprene, balata, polychloroprene, polynorbornene, polyoctenamer, polypentenamer, butyl rubber, EPR, EPDM, styrene-butadiene, and the like.

Suitable thermoplastic materials for forming layers include, but are not limited to, ionomer compositions containing acid groups that are at least partially-neutralized. Suitable ionomer compositions include partially-neutralized ionomers and highly-neutralized ionomers (HNPs), including ionomers formed from blends of two or more partially-neutralized ionomers, blends of two or more highly-neutralized ionomers, and blends of one or more partially-neutralized ionomers with one or more highly-neutralized ionomers. For purposes of the present disclosure, “HNP” refers to an acid copolymer after at least 70% of all acid groups present in the composition are neutralized. Preferred ionomers are salts of O/X- and O/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈ α,β-ethylenically unsaturated carboxylic acid, and Y is a softening monomer. O is preferably selected from ethylene and propylene. X is preferably selected from methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid. Methacrylic acid and acrylic acid are particularly preferred. Y is preferably selected from (meth) acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1 to 8 carbon atoms, including, but not limited to, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.

Preferred O/X and O/X/Y-type copolymers include, without limitation, ethylene acid copolymers, such as ethylene/(meth)acrylic acid, ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylic acid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acid mono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate, ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate, ethylene/(meth)acrylic acid/methyl (meth)acrylate, ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and the like. The term, “copolymer,” as used herein, includes polymers having two types of monomers, those having three types of monomers, and those having more than three types of monomers. Preferred α, β-ethylenically unsaturated mono- or dicarboxylic acids are (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconic acid. (Meth) acrylic acid is most preferred. As used herein, “(meth) acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” means methacrylate and/or acrylate.

Suitable acid polymers for forming the ionomer composition also include acid polymers that are already partially neutralized. Examples of suitable partially neutralized acid polymers include, but are not limited to, Surlyn® ionomers, commercially available from E. I. du Pont de Nemours and Company; AClyn® ionomers, commercially available from Honeywell International Inc.; and Iotek® ionomers, commercially available from ExxonMobil Chemical Company. Also suitable are DuPont® HPF 1000 and DuPont® HPF 2000, ionomeric materials commercially available from E. I. du Pont de Nemours and Company. In some embodiments, very low modulus ionomer- (“VLMI-”) type ethylene-acid polymers are particularly suitable for forming the ionomer composition, such as Surlyn® 6320, Surlyn® 8120, Surlyn® 8320, and Surlyn® 9320, commercially available from E. I. du Pont de Nemours and Company.

The α-olefin is typically present in the O/X or O/X/Y-type copolymer in an amount of 15 wt. % or greater, or 25 wt. % or greater, or 40 wt. % or greater, or 60 wt. % or greater, based on the total weight of the acid copolymer. The acid is typically present in the acid copolymer in an amount of 6 wt. % or greater, or 9 wt. % or greater, or 10 wt. % or greater, or 11 wt. % or greater, or 15 wt. % or greater, or 16 wt. % or greater, or in an amount within a range having a lower limit of 1 or 4 or 5 or 6 or 8 or 10 or 11 or 12 or 15 or 16 or 20 wt. % and an upper limit of 15 or 16 or 17 or 19 or 20 or 20.5 or 21 or 25 or 26 or 30 or 35 or 40 wt. %, based on the total weight of the acid copolymer. The optional softening monomer is typically present in the acid copolymer in an amount within a range having a lower limit of 0 or 1 or 3 or 5 or 11 or 15 or 20 wt. % and an upper limit of 23 or 25 or 30 or 35 or 50 wt. %, based on the total weight of the acid copolymer.

Additional suitable acid polymers are more fully described, for example, in U.S. Pat. Nos. 5,691,418, 6,562,906, 6,653,382, 6,777,472, 6,762,246, 6,815,480, and 6,953,820 and U.S. Patent Application Publication Nos. 2005/0148725, 2005/0049367, 2005/0020741, 2004/0220343, and 2003/0130434, the entire disclosures of which are hereby incorporated herein by reference.

The O/X or O/X/Y-type copolymer is at least partially neutralized with a cation source, optionally in the presence of a high molecular weight organic acid, such as those disclosed in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference, such that at least 70%, preferably at least 80%, more preferably at least 90%, more preferably at least 95%, and even more preferably 100%, of all acid groups present are neutralized. In a particular embodiment, the cation source is present in an amount sufficient to neutralize, theoretically, greater than 100%, or 105% or greater, or 110% or greater, or 115% or greater, or 120% or greater, or 125% or greater, or 200% or greater, or 250% or greater of all acid groups present in the composition. The acid copolymer can be reacted with the optional high molecular weight organic acid and the cation source simultaneously, or prior to the addition of the cation source.

Suitable cation sources include, but are not limited to, metal ion sources, such as compounds of alkali metals, alkaline earth metals, transition metals, and rare earth elements; ammonium salts and monoamine salts; and combinations thereof. Preferred cation sources are compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, lead, tin, aluminum, nickel, chromium, lithium, and rare earth metals. Methods of preparing ionomers, and the acid polymers on which ionomers are based, are disclosed, for example, in U.S. Pat. Nos. 3,264,272, and 4,351,931, and U.S. Patent Application Publication No. 2002/0013413.

Suitable high molecular weight organic acids are aliphatic organic acids, aromatic organic acids, saturated monofunctional organic acids, unsaturated monofunctional organic acids, multi-unsaturated monofunctional organic acids, and dimerized derivatives thereof. Particular examples of suitable organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, dimerized derivatives thereof, and combinations thereof. Salts of high molecular weight organic acids comprise the salts, particularly the barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, stontium, titanium, tungsten, magnesium, and calcium salts, of aliphatic organic acids, aromatic organic acids, saturated monofunctional organic acids, unsaturated monofunctional organic acids, multi-unsaturated monofunctional organic acids, dimerized derivatives thereof, and combinations thereof. Suitable organic acids and salts thereof are more fully described, for example, in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, the HNP composition comprises an organic acid salt in an amount of 20 phr or greater, or 25 phr or greater, or 30 phr or greater, or 35 phr or greater, or 40 phr or greater.

The ionomer composition optionally comprises at least one additional polymer component selected from partially neutralized ionomers as disclosed, for example, in U.S. Patent Application Publication No. 2006/0128904, the entire disclosure of which is hereby incorporated herein by reference; bimodal ionomers, such as those disclosed in U.S. Patent Application Publication No. 2004/0220343 and U.S. Pat. Nos. 6,562,906, 6,762,246, 7,273,903, 8,193,283, 8,410,219, and 8,410,220, the entire disclosures of which are hereby incorporated herein by reference, and particularly Surlyn® AD 1043, 1092, and 1022 ionomer resins, commercially available from E. I. du Pont de Nemours and Company; ionomers modified with rosins, such as those disclosed in U.S. Patent Application Publication No. 2005/0020741, the entire disclosure of which is hereby incorporated by reference; soft and resilient ethylene copolymers, such as those disclosed U.S. Patent Application Publication No. 2003/0114565, the entire disclosure of which is hereby incorporated herein by reference; polyolefins, such as linear, branched, or cyclic, C₂-C₄₀ olefins, particularly polymers comprising ethylene or propylene copolymerized with one or more C₂-C₄₀ olefins, C₃-C₂₀ α-olefins, or C₃-C₁₀ α-olefins; polyamides; polyesters; polyethers; polycarbonates; polysulfones; polyacetals; polylactones; acrylonitrile-butadiene-styrene resins; polyphenylene oxide; polyphenylene sulfide; styrene-acrylonitrile resins; styrene maleic anhydride; polyimides; aromatic polyketones; ionomers and ionomeric precursors, acid copolymers, and conventional HNPs, such as those disclosed in U.S. Pat. Nos. 6,756,436, 6,894,098, and 6,953,820, the entire disclosures of which are hereby incorporated herein by reference; polyurethanes; grafted and non-grafted metallocene-catalyzed polymers, such as single-site catalyst polymerized polymers, high crystalline acid polymers, cationic ionomers, and combinations thereof; natural and synthetic rubbers, including, but not limited to, ethylene propylene rubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic block copolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber, halobutyl rubber, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, natural rubber, polyisoprene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber (such as ethylene-alkyl acrylates and ethylene-alkyl methacrylates, and, more specifically, ethylene-ethyl acrylate, ethylene-methyl acrylate, and ethylene-butyl acrylate), chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and polybutadiene rubber (cis and trans). Additional suitable blend polymers include those described in U.S. Pat. No. 5,981,658, for example at column 14, lines 30 to 56, the entire disclosure of which is hereby incorporated herein by reference. The blend may be produced by post-reactor blending, by connecting reactors in series to make reactor blends, or by using more than one catalyst in the same reactor to produce multiple species of polymer. The polymers may be mixed prior to being put into an extruder, or they may be mixed in an extruder. In a particular embodiment, the ionomer composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of greater than 50 wt %, or an amount within a range having a lower limit of 50 or 55 or 60 or 65 or 70 and an upper limit of 80 or 85 or 90, based on the combined weight of the acid copolymer and the non-acid polymer. In another particular embodiment, the ionomer composition comprises an acid copolymer and an additional polymer component, wherein the additional polymer component is a non-acid polymer present in an amount of less than 50 wt %, or an amount within a range having a lower limit of 10 or 15 or 20 or 25 or 30 and an upper limit of 40 or 45 or 50, based on the combined weight of the acid copolymer and the non-acid polymer.

Suitable HNP compositions are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,815,480, 6,894,098, 6,919,393, 6,953,820, 6,994,638, 7,375,151, the entire disclosures of which are hereby incorporated herein by reference.

Non-limiting examples of suitable commercially available ionomers and other thermoplastic materials that can be used in accordance with this invention are Surlyn® ionomers and DuPont® HPF 1000 and HPF 2000 highly neutralized polymers, commercially available from E. I. du Pont de Nemours and Company; Clarix® ionomers, commercially available from A. Schulman, Inc.; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; and Amplify® IO ionomers, commercially available from The Dow Chemical Company; Amplify® GR functional polymers and Amplify® TY functional polymers, commercially available from The Dow Chemical Company; Fusabond® functionalized polymers, commercially available from E. I. du Pont de Nemours and Company; Exxelor® maleic anhydride grafted polymers, commercially available from ExxonMobil Chemical Company; ExxonMobil® PP series polypropylene impact copolymers, commercially available from ExxonMobil Chemical Company; Vistamaxx® propylene-based elastomers, commercially available from ExxonMobil Chemical Company; Exact® plastomers, commercially available from ExxonMobil Chemical Company; Santoprene® thermoplastic vulcanized elastomers, commercially available from ExxonMobil Chemical Company; Kraton® styrenic block copolymers, commercially available from Kraton Performance Polymers Inc.; Septon® styrenic block copolymers, commercially available from Kuraray Co., Ltd.; Lotader® ethylene acrylate based polymers, commercially available from Arkema Corporation; Polybond® grafted polyethylenes and polypropylenes, commercially available from Chemtura Corporation; Pebax® polyether and polyester amides, commercially available from Arkema Inc.; polyester-based thermoplastic elastomers, such as Hytrel® polyester elastomers, commercially available from E. I. du Pont de Nemours and Company, and Riteflex® polyester elastomers, commercially available from Ticona; Estane® thermoplastic polyurethanes, commercially available from The Lubrizol Corporation; Grivory® polyamides and Grilamid® polyamides, commercially available from EMS Grivory; Zytel® polyamide resins and Elvamide® nylon multipolymer resins, commercially available from E. I. du Pont de Nemours and Company; Elvaloy® acrylate copolymer resins, commercially available from E. I. du Pont de Nemours and Company; Elastollan® polyurethane-based thermoplastic elastomers, commercially available from BASF; Xylex® polycarbonate/polyester blends, commercially available from SABIC Innovative Plastics; and combinations of two or more thereof.

As discussed above, the acid is typically present in the O/X or O/X/Y-type copolymer in an amount of 6 wt. % or greater. “Low acid” and “high acid” ionomeric copolymers, as well as blends of such ionomers, may be used. In general, low acid ionomers are considered to be those containing 16 wt. % or less of acid moieties, whereas high acid ionomers are considered to be those containing greater than 16 wt. % of acid moieties. The acidic groups in the acid copolymers are partially or totally-neutralized with a cation source. Suitable cation sources include metal cations and salts thereof, organic amine compounds, ammonium, and combinations thereof. Suitable cation sources include, for example, metal cations and salts thereof, wherein the metal is preferably lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper, or a combination thereof. The metal cation salts provide the cations capable of neutralizing (at varying levels) the carboxylic acids of the ethylene acid copolymer and fatty acids, if present, as discussed further below. These include, for example, the sulfate, carbonate, acetate, oxide, or hydroxide salts of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper, or a combination thereof. Preferred metal cation salts are calcium and magnesium-based salts. High surface area cation particles such as micro and nano-scale cation particles are preferred. The amount of cation used in the composition is readily determined based on desired level of neutralization.

For example, olefin acid copolymer ionomer resins having acid groups that are neutralized from about 10 percent or greater may be used. In one ionomer composition, the acid groups are partially-neutralized. That is, the neutralization level is from about 10% to about 70%, more preferably 20% to 60%, and most preferably 30 to 50%. These ionomer compositions, containing acid groups neutralized to 70% or less, may be referred to ionomers having relatively low neutralization levels or partial-neutralization. On the other hand, the ionomer composition may contain acid groups that are highly or fully-neutralized. In these HNPs, the neutralization level is greater than 70%, preferably at least 90%, and even more preferably at least 100%. In another embodiment, an excess amount of neutralizing agent, that is, an amount greater than the stoichiometric amount needed to neutralize the acid groups, may be used. That is, the acid groups may be neutralized to 100% or greater, for example 110% or 120% or greater.

When the α-olefin monomer is ethylene, such copolymers are referred to herein as E/X-type copolymers and when a softening monomer is included, such copolymers are referred to herein as E/X/Y-type copolymers, wherein E is ethylene; X is a C₃ to C₈ α, β-ethylenically unsaturated mono- or dicarboxylic acid; and Y is a softening monomer. The softening monomer is typically an alkyl (meth) acrylate, wherein the alkyl groups have from 1 to 8 carbon atoms. Preferred E/X/Y-type copolymers are those wherein X is (meth) acrylic acid and/or Y is selected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. More preferred E/X/Y-type copolymers are ethylene/(meth) acrylic acid/n-butyl acrylate, ethylene/(meth) acrylic acid/methyl acrylate, and ethylene/(meth) acrylic acid/ethyl acrylate.

The amount of ethylene in the E/X and E/X/Y-type copolymers is typically at least 15 wt. %, preferably at least 25 wt. %, more preferably least 40 wt. %, and even more preferably at least 60 wt. %, based on total weight of the copolymer. The amount of C₃ to C₈ α, β-ethylenically unsaturated mono- or dicarboxylic acid in the ethylene acid copolymer is typically from 1 wt. % to 35 wt. %, preferably from 5 wt. % to 30 wt. %, more preferably from 5 wt. % to 25 wt. %, and even more preferably from 10 wt. % to 20 wt. %, based on total weight of the copolymer. The amount of optional softening monomer in the ethylene acid copolymer is typically from 0 wt. % to 50 wt. %, preferably from 5 wt. % to 40 wt. %, more preferably from 10 wt. % to 35 wt. %, and even more preferably from 20 wt. % to 30 wt. %, based on total weight of the copolymer. As discussed above, “low acid” and “high acid” ionomeric polymers, as well as blends of such ionomers, may be used. In general, low acid ionomers are considered to be those containing 16 wt. % or less of acid moieties, whereas high acid ionomers are considered to be those containing greater than 16 wt. % of acid moieties.

As discussed above, the acidic groups in the E/X and E/X/Y-type copolymer ionomers are partially or totally neutralized with a cation source. Suitable cation sources include metal cations and salts thereof, organic amine compounds, ammonium, and combinations thereof. Preferred cation sources are metal cations and salts thereof, wherein the metal is preferably lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper, or a combination thereof. The metal cation salts provide the cations capable of neutralizing (at varying levels) the carboxylic acids of the ethylene acid copolymer and fatty acids, if present, as discussed further below. These include, for example, the sulfate, carbonate, acetate, oxide, or hydroxide salts of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, manganese, nickel, chromium, copper, or a combination thereof. Preferred metal cation salts are calcium and magnesium-based salts. High surface area cation particles such as micro and nano-scale cation particles are preferred. The amount of cation used in the composition is readily determined based on desired level of neutralization.

For example, ethylene acid copolymers having acid groups that are neutralized from about 10 percent or greater may be used. In one ethylene acid copolymer composition, the acid groups are partially-neutralized. That is, the neutralization level is from about 10% to about 70%, more preferably 20% to 60%, and most preferably 30 to 50%. These ethylene acid copolymer compositions, containing acid groups neutralized to 70% or less, may be referred to ionomers having relatively low neutralization levels or partial-neutralization. On the other hand, the ethylene acid copolymer composition may contain acid groups that are highly or fully-neutralized. In these HNPs, the neutralization level is greater than 70%, preferably at least 90%, and even more preferably at least 100%. In another embodiment, an excess amount of neutralizing agent, that is, an amount greater than the stoichiometric amount needed to neutralize the acid groups, may be used. That is, the acid groups may be neutralized to 100% or greater, for example 110% or 120% or greater. In one preferred embodiment, a high acid ethylene acid copolymer containing about 19 to 20 wt. % methacrylic or acrylic acid is neutralized with zinc and sodium cations to a 95% neutralization level.

“Ionic plasticizers” such as organic acids or salts of organic acids, particularly fatty acids, may be added to any of the ionomer resins if needed. Such ionic plasticizers are used to make conventional ionomer composition more processable as described in Rajagopalan et al., U.S. Pat. No. 6,756,436, the disclosure of which is hereby incorporated by reference. In one preferred embodiment, the thermoplastic ionomer composition, containing acid groups neutralized to 70% or less, does not include a fatty acid or salt thereof, or any other ionic plasticizer. On the other hand, the thermoplastic ionomer composition, containing acid groups neutralized to greater than 70%, includes an ionic plasticizer, particularly a fatty acid or salt thereof. For example, the ionic plasticizer may be added in an amount of 0.5 to 10 pph, more preferably 1 to 5 pph. The organic acids may be aliphatic, mono- or multi-functional (saturated, unsaturated, or multi-unsaturated) organic acids. Salts of these organic acids may also be employed. Suitable fatty acid salts include, for example, metal stearates, laureates, oleates, palmitates, pelargonates, and the like. For example, fatty acid salts such as zinc stearate, calcium stearate, magnesium stearate, barium stearate, and the like can be used. The salts of fatty acids are generally fatty acids neutralized with metal ions. The metal cation salts provide the cations capable of neutralizing (at varying levels) the carboxylic acid groups of the fatty acids. Examples include the sulfate, carbonate, acetate and hydroxide salts of metals such as barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, or calcium, and blends thereof. It is preferred the organic acids and salts be relatively non-migratory (they do not bloom to the surface of the polymer under ambient temperatures) and non-volatile (they do not volatilize at temperatures required for melt-blending).

As noted above, the final ionomer compositions may contain additional materials such as, for example, a small amount of ionic plasticizer, which is particularly effective at improving the processability of highly-neutralized ionomers. For example, the ionic plasticizer may be added in an amount of 0.5 to 10 pph, more preferably 1 to 5 pph. In addition to the fatty acids and salts of fatty acids discussed above, other suitable ionic plasticizers include, for example, polyethylene glycols, waxes, bis-stearamides, minerals, and phthalates. In another embodiment, an amine or pyridine compound is used, preferably in addition to a metal cation. Suitable examples include, for example, ethylamine, methylamine, diethylamine, tert-butylamine, dodecylamine, and the like.

The ionomer compositions may contain a wide variety of fillers and some of these fillers may be used to adjust the specific gravity of the composition as needed. High surface-area fillers that have an affinity for the acid groups in ionomer may be used. In particular, fillers such as particulate, fibers, or flakes having cationic nature such that they may also contribute to the neutralization of the ionomer are suitable. For example, aluminum oxide, zinc oxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc carbonate, barium carbonate, tungsten, tungsten carbide, and lead silicate fillers may be used. Also, silica, fumed silica, and precipitated silica, such as those sold under the tradename, HISIL™, from PPG Industries, carbon black, carbon fibers, and nano-scale materials such as nanotubes, nanoflakes, nanofillers, and nanoclays may be used. Relatively heavy-weight fillers also may be added to the ionomer compositions including, but not limited to, particulate, powders, fibers and flakes of heavy metals such as copper, nickel, tungsten, brass, steel, magnesium, molybdenum, cobalt, lead, tin, silver, gold, and platinum, and alloys thereof. Steel materials also can be added. In other instances, it may be desirable to add relatively light-weight metals such as titanium and aluminum alloys thereof. Other additives and fillers include, but are not limited to, chemical blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, titanium dioxide, acid copolymer wax, surfactants, rubber regrind (recycled core material), clay, mica, talc, glass flakes, milled glass, and mixtures thereof. Suitable additives are more fully described in, for example, Rajagopalan et al., U.S. Patent Application Publication No. 2003/0225197, the entire disclosure of which is hereby incorporated herein by reference. In a particular embodiment, the total amount of additive(s) and filler(s) present in the final thermoplastic ionomeric composition is 25 wt. % or less, or 20 wt. % or less, or 15 wt. % or less, or 12 wt. % or less, or 10 wt. % or less, or 9 wt. % or less, or 6 wt. % or less, or 5 wt. % or less, or 4 wt. % or less, or 3 wt. % or less, based on total weight of the ionomeric composition.

The acid copolymer ionomer is used in an amount of at least about 5% by weight based on total weight of composition and is generally present in an amount of about 5% to about 100%, or an amount within a range having a lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upper limit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, the concentration of acid copolymer is about 40 to about 95 weight percent.

In a particular embodiment, a thermoplastic layer is formed from an HNP composition, wherein the HNP composition is formed by blending an acid polymer, a non-acid polymer, a cation source, and a fatty acid or metal salt thereof. For purposes of the present invention, maleic anhydride modified polymers are defined herein as a non-acid polymer despite having anhydride groups that can ring-open to the acid form during processing of the polymer to form the HNP compositions herein. The maleic anhydride groups are grafted onto a polymer, are present at relatively very low levels, and are not part of the polymer backbone, as is the case with the acid polymers, which are exclusively E/X and E/X/Y copolymers of ethylene and an acid, particularly methacrylic acid and acrylic acid.

In a particular aspect of this embodiment, the acid polymer is selected from ethylene-acrylic acid and ethylene-methacrylic acid copolymers, optionally containing a softening monomer selected from n-butyl acrylate and iso-butyl acrylate. The acid polymer preferably has an acid content with a range having a lower limit of 2 or 10 or 15 or 16 mol % and an upper limit of 20 or 25 or 26 or 30 mol %. Examples of particularly suitable commercially available acid polymers include, but are not limited to, those given in Table 1A below.

TABLE 1A Melt Index Softening (2.16 kg, Acid Monomer 190° C., Acid Polymer (wt %) (wt %) g/10 min) Nucrel ® 9-1 methacrylic acid n-butyl acrylate 25  (9.0) (23.5) Nucrel ® 599 methacrylic acid none 450 (10.0) Nucrel ® 960 methyacrylic acid none 60 (15.0) Nucrel ® 0407 methacrylic acid none 7.5  (4.0) Nucrel ® 0609 methacrylic acid none 9  (6.0) Nucrel ® 1214 methacrylic acid none 13.5 (12.0) Nucrel ® 2906 methacrylic acid none 60 (19.0) Nucrel ® 2940 methacrylic acid none 395 (19.0) Nucrel ® 30707 acrylic acid none 7  (7.0) Nucrel ® 31001 acrylic acid none 1.3  (9.5) Nucrel ® AE methacrylic acid isobutyl acrylate 11  (2.0)  (6.0) Nucrel ® 2806 acrylic acid none 60 (18.0) Nucrel ® 0403 methacrylic acid none 3  (4.0) Nucrel ® 925 methacrylic acid none 25 (15.0) Escor ® AT-310 acrylic acid methyl acrylate 6  (6.5)  (6.5) Escor ® AT-325 acrylic acid methyl acrylate 20  (6.0) (20.0) Escor ® AT-320 acrylic acid methyl acrylate 5  (6.0) (18.0) Escor ® 5070 acrylic acid none 30  (9.0) Escor ® 5100 acrylic acid none 8.5 (11.0) Escor ® 5200 acrylic acid none 38 (15.0) A-C ® 5120 acrylic acid none not reported (15)   A-C ® 540 acrylic acid none not reported (5)  A-C ® 580 acrylic acid none not reported (10)   Primacor ® 3150 acrylic acid none 5.8  (6.5) Primacor ® 3330 acrylic acid none 11  (3.0) Primacor ® 5985 acrylic acid none 240 (20.5) Primacor ® 5986 acrylic acid none 300 (20.5) Primacor ® 5980I acrylic acid none 300 (20.5) Primacor ® 5990I acrylic acid none 1300 (20.0) XUS 60751.17 acrylic acid none 600 (19.8) XUS 60753.02L acrylic acid none 60 (17.0) Nucrel ® acid polymers are commercially available from E. I. du Pont de Nemours and Company. Escor ® acid polymers are commercially available from ExxonMobil Chemical Company. A-C ® acid polymers are commercially available from Honeywell International Inc. Primacor ® acid polymers and XUS acid polymers are commercially available from The Dow Chemical Company.

In another particular aspect of this embodiment, the non-acid polymer is an elastomeric polymer. Suitable elastomeric polymers include, but are not limited to:

-   -   (a) ethylene-alkyl acrylate polymers, particularly         polyethylene-butyl acrylate, polyethylene-methyl acrylate, and         polyethylene-ethyl acrylate;     -   (b) metallocene-catalyzed polymers;     -   (c) ethylene-butyl acrylate-carbon monoxide polymers and         ethylene-vinyl acetate-carbon monoxide polymers;     -   (d) polyethylene-vinyl acetates;     -   (e) ethylene-alkyl acrylate polymers containing a cure site         monomer;     -   (f) ethylene-propylene rubbers and ethylene-propylene-diene         monomer rubbers;     -   (g) olefinic ethylene elastomers, particularly ethylene-octene         polymers, ethylene-butene polymers, ethylene-propylene polymers,         and ethylene-hexene polymers;     -   (h) styrenic block copolymers;     -   (i) polyester elastomers;     -   (j) polyamide elastomers;     -   (k) polyolefin rubbers, particularly polybutadiene,         polyisoprene, and styrene-butadiene rubber; and     -   (l) thermoplastic polyurethanes.

Examples of particularly suitable commercially available non-acid polymers include, but are not limited to, Lotader® ethylene-alkyl acrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, and particularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900 commercially available from Arkema Corporation; Elvaloy® AC ethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC 2116, AC3117, AC3427, and AC34035, commercially available from E. I. du Pont de Nemours and Company; Fusabond® elastomeric polymers, such as ethylene vinyl acetates, polyethylenes, metallocene-catalyzed polyethylenes, ethylene propylene rubbers, and polypropylenes, and particularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614, M603, E100, E158, E226, E265, E528, and E589, commercially available from E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenes and ethylene maleic anhydride copolymers, and particularly A-C 5180, A-C 575, A-C 573, A-C 655, and A-C 395, commercially available from Honeywell; Nordel® IP rubber, Elite® polyethylenes, Engage® elastomers, and Amplify® functional polymers, and particularly Amplify® GR 207, GR 208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA 100, commercially available from The Dow Chemical Company; Enable® metallocene polyethylenes, Exact® plastomers, Vistamaxx® propylene-based elastomers, and Vistalon® EPDM rubber, commercially available from ExxonMobil Chemical Company; Starflex® metallocene linear low density polyethylene, commercially available from LyondellBasell; Elvaloy® HP4051, HP441, HP661 and HP662 ethylene-butyl acrylate-carbon monoxide polymers and Elvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbon monoxide polymers, commercially available from E. I. du Pont de Nemours and Company; Evatane® ethylene-vinyl acetate polymers having a vinyl acetate content of from 18 to 42%, commercially available from Arkema Corporation; Elvax® ethylene-vinyl acetate polymers having a vinyl acetate content of from 7.5 to 40%, commercially available from E. I. du Pont de Nemours and Company; Vamac® G terpolymer of ethylene, methylacrylate and a cure site monomer, commercially available from E. I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commercially available from ExxonMobil Chemical Company; Kraton® styrenic block copolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT, commercially available from Kraton Performance Polymers Inc.; Septon® styrenic block copolymers, commercially available from Kuraray Co., Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069, and 556, commercially available from E. I. du Pont de Nemours and Company; Riteflex® polyester elastomers, commercially available from Celanese Corporation; Pebax® thermoplastic polyether block amides, and particularly Pebax® 2533, 3533, 4033, and 5533, commercially available from Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify® ethylene-propylene copolymer elastomers, and Infuse® olefin block copolymers, commercially available from The Dow Chemical Company; Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO 1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially available from ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularly Royaltuf® 498 maleic anhydride modified polyolefin based on an amorphous EPDM and Royaltuf® 485 maleic anhydride modified polyolefin based on an semi-crystalline EPDM, commercially available from Chemtura Corporation.

Additional examples of particularly suitable commercially available elastomeric polymers include, but are not limited to, those given in Table 1B below.

TABLE 1B Melt Index (2.16 kg, % Maleic 190° C., % Ester Anhydride g/10 min) Polyethylene Butyl Acrylates Lotader ® 3210 6 3.1 5 Lotader ® 4210 6.5 3.6 9 Lotader ® 3410 17 3.1 5 Lotryl ® 17BA04 16-19 0 3.5-4.5 Lotryl ® 35BA320 33-37 0 260-350 Elvaloy ® AC 3117 17 0 1.5 Elvaloy ® AC 3427 27 0 4 Elvaloy ® AC 34035 35 0 40 Polyethylene Methyl Acrylates Lotader ® 4503 19 0.3 8 Lotader ® 4603 26 0.3 8 Lotader ® AX 8900 26 8% GMA 6 Lotryl ® 24MA02 23-26 0 1-3 Elvaloy ® AC 12024S 24 0 20 Elvaloy ® AC 1330 30 0 3 Elvaloy ® AC 1335 35 0 3 Elvaloy ® AC 1224 24 0 2 Polyethylene Ethyl Acrylates Lotader ® 6200 6.5 2.8 40 Lotader ® 8200 6.5 2.8 200 Lotader ® LX 4110 5 3.0 5 Lotader ® HX 8290 17 2.8 70 Lotader ® 5500 20 2.8 20 Lotader ® 4700 29 1.3 7 Lotader ® 4720 29 0.3 7 Elvaloy ® AC 2116 16 0 1

The acid polymer and non-acid polymer are combined and reacted with a cation source, such that at least 80% of all acid groups present are neutralized. The present invention is not meant to be limited by a particular order for combining and reacting the acid polymer, non-acid polymer and cation source. In a particular embodiment, the fatty acid or metal salt thereof is used in an amount such that the fatty acid or metal salt thereof is present in the HNP composition in an amount of from 10 wt % to 60 wt %, or within a range having a lower limit of 10 or 20 or 30 or 40 wt % and an upper limit of 40 or 50 or 60 wt %, based on the total weight of the HNP composition. Suitable cation sources and fatty acids and metal salts thereof are further disclosed above.

In another particular aspect of this embodiment, the acid polymer is an ethylene-acrylic acid polymer having an acid content of 19 wt % or greater, the non-acid polymer is a metallocene-catalyzed ethylene-butene copolymer, optionally modified with maleic anhydride, the cation source is magnesium, and the fatty acid or metal salt thereof is magnesium oleate present in the composition in an amount of 20 to 50 wt %, based on the total weight of the composition.

Other suitable thermoplastic polymers that may be used to form layers include, but are not limited to, the following polymers, including homopolymers, copolymers, and derivatives thereof:

(a) polyesters, particularly those modified with a compatibilizing group such as sulfonate or phosphonate, including modified poly(ethylene terephthalate), modified poly(butylene terephthalate), modified poly(propylene terephthalate), modified poly(trimethylene terephthalate), modified poly(ethylene naphthenate), and those disclosed in U.S. Pat. Nos. 6,353,050, 6,274,298, and 6,001,930, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;

(b) polyamides, polyamide-ethers, and polyamide-esters, and those disclosed in U.S. Pat. Nos. 6,187,864, 6,001,930, and 5,981,654, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;

(c) polyurethanes, polyureas, polyurethane-polyurea hybrids, and blends of two or more thereof;

(d) fluoropolymers, such as those disclosed in U.S. Pat. Nos. 5,691,066, 6,747,110 and 7,009,002, the entire disclosures of which are hereby incorporated herein by reference, and blends of two or more thereof;

(e) polystyrenes, such as poly(styrene-co-maleic anhydride), acrylonitrile-butadiene-styrene, poly(styrene sulfonate), polyethylene styrene, and blends of two or more thereof;

(f) polyvinyl chlorides and grafted polyvinyl chlorides, and blends of two or more thereof;

(g) polycarbonates, blends of polycarbonate/acrylonitrile-butadiene-styrene, blends of polycarbonate/polyurethane, blends of polycarbonate/polyester, and blends of two or more thereof;

(h) polyethers, such as polyarylene ethers, polyphenylene oxides, block copolymers of alkenyl aromatics with vinyl aromatics and polyamicesters, and blends of two or more thereof;

(i) polyimides, polyetherketones, polyamideimides, and blends of two or more thereof; and

(j) polycarbonate/polyester copolymers and blends.

These thermoplastic polymers may be used by and in themselves to form a layer, or blends of thermoplastic polymers including the above-described polymers and ethylene acid copolymer ionomers may be used. It also is recognized that the ionomer compositions may contain a blend of two or more ionomers. For example, the composition may contain a 50/50 wt. % blend of two different highly-neutralized ethylene/methacrylic acid copolymers. In another version, the composition may contain a blend of one or more ionomers and a maleic anhydride-grafted non-ionomeric polymer. The non-ionomeric polymer may be a metallocene-catalyzed polymer. In another version, the composition contains a blend of a highly-neutralized ethylene/methacrylic acid copolymer and a maleic anhydride-grafted metallocene-catalyzed polyethylene. In yet another version, the composition contains a material selected from the group consisting of highly-neutralized ionomers optionally blended with a maleic anhydride-grafted non-ionomeric polymer; polyester elastomers; polyamide elastomers; and combinations of two or more thereof.

It also is recognized that thermoplastic materials can be “converted” into thermoset materials by cross-linking the polymer chains so they form a network structure, and such cross-linked thermoplastic materials may be used to form layers in accordance with this invention. For example, thermoplastic polyolefins such as linear low density polyethylene (LLDPE), low density polyethylene (LDPE), and high density polyethylene (HDPE) may be cross-linked to form bonds between the polymer chains. The cross-linked thermoplastic material typically has improved physical properties and strength over non-cross-linked thermoplastics, particularly at temperatures above the crystalline melting point. Preferably a partially or fully-neutralized ionomer, as described above, is covalently cross-linked to render it into a thermoset composition (that is, it contains at least some level of covalent, irreversible cross-links). Thermoplastic polyurethanes and polyureas also may be converted into thermoset materials in accordance with the present invention.

The cross-linked thermoplastic material may be created by exposing the thermoplastic to: 1) a high-energy radiation treatment, such as electron beam or gamma radiation, such as disclosed in U.S. Pat. No. 5,891,973, which is incorporated by reference herein, 2) lower energy radiation, such as ultra-violet (UV) or infra-red (IR) radiation; 3) a solution treatment, such as an isocyanate or a silane; 4) incorporation of additional free radical initiator groups in the thermoplastic prior to molding; and/or 5) chemical modification, such as esterification or saponification, to name a few.

Modifications in thermoplastic polymeric structure of thermoplastic can be induced by a number of methods, including exposing the thermoplastic material to high-energy radiation or through a chemical process using peroxide. Radiation sources include, but are not limited to, gamma-rays, electrons, neutrons, protons, x-rays, helium nuclei, or the like. Gamma radiation, typically using radioactive cobalt atoms and allows for considerable depth of treatment, if necessary. For layers requiring lower depth of penetration, electron-beam accelerators or UV and IR light sources can be used. Useful UV and IR irradiation methods are disclosed in U.S. Pat. Nos. 6,855,070 and 7,198,576, which are incorporated herein by reference. The thermoplastic layers may be irradiated at dosages greater than 0.05 Mrd, preferably ranging from 1 Mrd to 20 Mrd, more preferably from 2 Mrd to 15 Mrd, and most preferably from 4 Mrd to 10 Mrd. In one preferred embodiment, the layer may be irradiated at a dosage from 5 Mrd to 8 Mrd and in another preferred embodiment, the layer may be irradiated with a dosage from 0.05 Mrd to 3 Mrd, more preferably 0.05 Mrd to 1.5 Mrd.

For example, a thermoplastic layer may be converted to a thermoset layer by moving an assembly including the layer slowly move along a channel. Radiation from a radiation source, such as gamma rays, is allowed to contact the surface of the layer. The source is positioned to provide a generally uniform dose of radiation to the assembly including the layer as they roll along the channel. The speed of the assembly including the layer as it passes through the radiation source is easily controlled to ensure the assembly including the layer receives sufficient dosage to create the desired hardness gradient. The assembly including the layer is irradiated with a dosage of 1 or more Mrd, more preferably 2 Mrd to 15 Mrd. The intensity of the dosage is typically in the range of 1 MeV to 20 MeV. For thermoplastic resins having a reactive group (e.g., ionomers, thermoplastic urethanes, and the like), treating a thermoplastic layer in a chemical solution of an isocyanate or an amine affects cross-linking and provides a harder surface and subsequent hardness gradient. Incorporation of peroxide or other free-radical initiator in the thermoplastic polymer, prior to molding or forming, also allows for heat curing on the molded to create the desired hardness gradient. By proper selection of time/temperature, an annealing process can be used to create a gradient. Suitable annealing and/or peroxide (free radical) methods are such as disclosed in U.S. Pat. Nos. 5,274,041 and 5,356,941, respectively, which are incorporated by reference herein. Additionally, silane or amino-silane crosslinking may also be employed as disclosed in U.S. Pat. No. 7,279,529, the disclosure of which incorporated herein by reference. The assembly including the layer may be chemically treated in a solution, such as a solution containing one or more isocyanates, to form the desired “positive hardness gradient.” The assembly including the layer are typically exposed to the solution containing the isocyanate by immersing them in a bath at a particular temperature for a given time. Exposure time should be greater than 1 minute, preferably from 1 minute to 120 minutes, more preferably 5 minutes to 90 minutes, and most preferably 10 minutes to 60 minutes. In one preferred embodiment, the assembly including the layer is immersed in the treating solution from 15 minutes to 45 minutes, more preferably from 20 minutes to 40 minutes, and most preferably from 25 minutes to 30 minutes.

The assembly including the layer may be chemically treated in a solution, such as a solution containing one or more isocyanates, to form the desired “positive hardness gradient.” The assembly including the layer is typically exposed to the solution containing the isocyanate by immersing them in a bath at a particular temperature for a given time. Exposure time should be greater than 1 minute, preferably from 1 minute to 120 minutes, more preferably 5 minutes to 90 minutes, and most preferably 10 minutes to 60 minutes. In one preferred embodiment, the assembly including the layer is immersed in the treating solution from 15 minutes to 45 minutes, more preferably from 20 minutes to 40 minutes, and most preferably from 25 minutes to 30 minutes. Both irradiative and chemical methods promote molecular bonding, or cross-links, within the TP polymer. Radiative methods permit cross-linking and grafting in situ on finished products and cross-linking occurs at lower temperatures with radiation than with chemical processing. Chemical methods depend on the particular polymer, the presence of modifying agents, and variables in processing, such as the level of irradiation. Significant property benefits in the thermoplastic materials can be attained and include, but are not limited to, improved thermomechanical properties; lower permeability and improved chemical resistance; reduced stress cracking; and overall improvement in physical toughness.

Additional embodiments involve the use of plasticizers to treat the layers, thereby creating a softer outer portion of the layer for a “negative” hardness gradient. The plasticizer may be reactive (such as higher alkyl acrylates) or non-reactive (that is, phthalates, dioctylphthalate, or stearamides, etc). Other suitable plasticizers include, but are not limited to, oxa acids, fatty amines, fatty amides, fatty acid esters, phthalates, adipates, and sebacates. Oxa acids are preferred plasticizers, more preferably those having at least one or two acid functional groups and a variety of different chain lengths. Preferred oxa acids include 3,6-dioxaheptanoic acid, 3,6,9-trioxadecanoic acid, diglycolic acid, 3,6,9-trioxaundecanoic acid, polyglycol diacid, and 3,6-dioxaoctanedioic acid, such as those commercially available from Archimica of Wilmington, Del. Any means of chemical degradation will also result in a “negative” hardness gradient. Chemical modifications such as esterification or saponification are also suitable for modification of the thermoplastic layer surface and can result in the desired “positive hardness gradient.

Core Structure

The hardness of the core sub-assembly (inner core and outer core layer) is an important property. In general, cores with relatively high hardness values have higher compression and tend to have good durability and resiliency. However, some high compression balls are stiff and this may have a detrimental effect on shot control and placement. Thus, the optimum balance of hardness in the core sub-assembly needs to be attained, which may be coordinated with the hardness and other properties of the foamed intermediate layer.

In one preferred golf ball, the inner core (center) has a “positive” hardness gradient (that is, the outer surface of the inner core is harder than its geometric center); and the outer core layer has a “positive” hardness gradient (that is, the outer surface of the outer core layer is harder than the inner surface of the outer core layer.) In such cases where both the inner core and outer core layer each has a “positive” hardness gradient, the outer surface hardness of the outer core layer is preferably greater than the hardness of the geometric center of the inner core. In one preferred version, the positive hardness gradient of the inner core is in the range of about 2 to about 40 Shore C units and even more preferably about 10 to about 25 Shore C units; while the positive hardness gradient of the outer core is in the range of about 2 to about 20 Shore C and even more preferably about 3 to about 10 Shore C.

In an alternative version, the inner core may have a positive hardness gradient; and the outer core layer may have a “zero” hardness gradient (that is, the hardness values of the outer surface of the outer core layer and the inner surface of the outer core layer are substantially the same) or a “negative” hardness gradient (that is, the outer surface of the outer core layer is softer than the inner surface of the outer core layer.) For example, in one version, the inner core has a positive hardness gradient; and the outer core layer has a negative hardness gradient in the range of about 2 to about 25 Shore C. In a second alternative version, the inner core may have a zero or negative hardness gradient; and the outer core layer may have a positive hardness gradient. Still yet, in another embodiment, both the inner core and outer core layers have zero or negative hardness gradients.

In general, hardness gradients are further described in Bulpett et al., U.S. Pat. Nos. 7,537,529 and 7,410,429, the disclosures of which are hereby incorporated by reference. Methods for measuring the hardness of the inner core and outer core layers along with other layers in the golf ball and determining the hardness gradients of the various layers are described in further detail below. The core layers have positive, negative, or zero hardness gradients defined by hardness measurements made at the outer surface of the inner core (or outer surface of the outer core layer) and radially inward towards the center of the inner core (or inner surface of the outer core layer). These measurements are made typically at 2-mm increments as described in the test methods below. In general, the hardness gradient is determined by subtracting the hardness value at the innermost portion of the component being measured (for example, the center of the inner core or inner surface of the outer core layer) from the hardness value at the outer surface of the component being measured (for example, the outer surface of the inner core or outer surface of the outer core layer).

Positive Hardness Gradient.

For example, if the hardness value of the outer surface of the inner core is greater than the hardness value of the inner core's geometric center (that is, the inner core has a surface harder than its geometric center), the hardness gradient will be deemed “positive” (a larger number minus a smaller number equals a positive number.) For example, if the outer surface of the inner core has a hardness of 67 Shore C and the geometric center of the inner core has a hardness of 60 Shore C, then the inner core has a positive hardness gradient of 7. Likewise, if the outer surface of the outer core layer has a greater hardness value than the inner surface of the outer core layer, the given outer core layer will be considered to have a positive hardness gradient.

Negative Hardness Gradient. On the other hand, if the hardness value of the outer surface of the inner core is less than the hardness value of the inner core's geometric center (that is, the inner core has a surface softer than its geometric center), the hardness gradient will be deemed “negative.” For example, if the outer surface of the inner core has a hardness of 68 Shore C and the geometric center of the inner core has a hardness of 70 Shore C, then the inner core has a negative hardness gradient of 2. Likewise, if the outer surface of the outer core layer has a lesser hardness value than the inner surface of the outer core layer, the given outer core layer will be considered to have a negative hardness gradient.

Zero Hardness Gradient.

In another example, if the hardness value of the outer surface of the inner core is substantially the same as the hardness value of the inner core's geometric center (that is, the surface of the inner core has about the same hardness as the geometric center), the hardness gradient will be deemed “zero.” For example, if the outer surface of the inner core and the geometric center of the inner core each has a hardness of 65 Shore C, then the inner core has a zero hardness gradient. Likewise, if the outer surface of the outer core layer has a hardness value approximately the same as the inner surface of the outer core layer, the outer core layer will be considered to have a zero hardness gradient.

More particularly, the term, “positive hardness gradient” as used herein means a hardness gradient of positive 3 Shore C or greater, preferably 7 Shore C or greater, more preferably 10 Shore C, and even more preferably 20 Shore C or greater. The term, “zero hardness gradient” as used herein means a hardness gradient of less than 3 Shore C, preferably less than 1 Shore C and may have a value of zero or negative 1 to negative 10 Shore C. The term, “negative hardness gradient” as used herein means a hardness value of less than zero, for example, negative 3, negative 5, negative 7, negative 10, negative 15, or negative 20 or negative 25. The terms, “zero hardness gradient” and “negative hardness gradient” may be used herein interchangeably to refer to hardness gradients of negative 1 to negative 10.

The inner core preferably has a geometric center hardness (H_(inner core center)) of about 5 Shore D or greater. For example, the (H_(inner core center)) may be in the range of about 5 to about 88 Shore D and more particularly within a range having a lower limit of about 5 or 10 or 14 or 18 or 20 or 26 or 30 or 34 or 36 or 38 or 42 or 48 or 50 or 52 Shore D and an upper limit of about 54 or 56 or 58 or 60 or 62 or 64 or 68 or 70 or 74 or 76 or 80 or 82 or 84 or 88 Shore D. In another example, the center hardness of the inner core (H_(inner core center)), as measured in Shore C units, is preferably about 10 Shore C or greater; for example, the H_(inner core center) may have a lower limit of about 10 or 12 or 14 or 16 or 20 or 22 or 23 or 24 or 28 or 31 or 34 or 37 or 40 or 44 or 52 or 58 Shore C and an upper limit of about 46 or 48 or 50 or 51 or 53 or 55 or 58 or 61 or 62 or 65 or 68 or 71 or 74 or 76 or 78 or 79 or 80 or 84 or 90 Shore C. Concerning the outer surface hardness of the inner core (H_(inner core surface)), this hardness is preferably about 12 Shore D or greater or about 15 Shore D or greater; for example, the H_(inner core surface) may fall within a range having a lower limit of about 12 or 15 or 18 or 20 or 22 or 23 or 26 or 30 or 34 or 36 or 38 or 42 or 48 or 50 or 52 Shore D and an upper limit of about 54 or 56 or 58 or 60 or 62 or 70 or 72 or 75 or 78 or 80 or 82 or 84 or 86 or 90 Shore D. In one version, the outer surface hardness of the inner core (H_(inner core surface)), as measured in Shore C units, has a lower limit of about 13 or 15 or 18 or 20 or 22 or 24 or 27 or 28 or 30 or 32 or 34 or 38 or 44 or 47 or 48 or 58 or 60 or 70 or 74 Shore C and an upper limit of about 50 or 54 or 56 or 61 or 65 or 66 or 68 or 70 or 73 or 76 or 78 or 80 or 84 or 86 or 88 or 90 or 92 Shore C. In another version, the geometric center hardness (H_(inner core center)) is in the range of about 10 Shore C to about 50 Shore C; and the outer surface hardness of the inner core (R_(inner core surface)) is in the range of about 5 Shore C to about 50 Shore C or in the range of about 5 Shore C to about 48 Shore C.

On the other hand, the outer core layer preferably has an outer surface hardness (H_(outer surface of OC)) of about 40 Shore D or greater, and more preferably within a range having a lower limit of about 40 or 42 or 44 or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or 60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90 Shore D. The outer surface hardness of the outer core layer (H_(outer surface of OC)), as measured in Shore C units, preferably has a lower limit of about 40 or 42 or 43 or 45 or 48 or 50 or 54 or 58 or 60 or 63 or 65 or 67 or 70 or 72 or 73 or 76 Shore C, and an upper limit of about 78 or 80 or 84 or 85 or 87 or 88 or 89 or 90 or 92 or 95 Shore C. And, the inner surface of the outer core layer (H_(inner surface of OC)) preferably has a hardness of about 40 Shore D or greater, and more preferably within a range having a lower limit of about 40 or 42 or 44 or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or 60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90 Shore D. The inner surface hardness of the outer core layer (H_(inner surface of OC)), as measured in Shore C units, preferably has a lower limit of about 40 or 42 or 44 or 45 or 47 or 50 or 52 or 54 or 55 or 58 or 60 or 63 or 65 or 67 or 70 or 73 or 76 Shore C, and an upper limit of about 78 or 80 or 85 or 87 or 88 or 89 or 90 or 92 or 95 Shore C.

In one embodiment, the outer surface hardness of the outer core layer (H_(outer surface of OC)), is less than the outer surface hardness (H_(inner core surface)) of the inner core by at least 3 Shore C units and more preferably by at least 5 Shore C.

In another embodiment, the outer surface hardness of the outer core layer (H_(outer surface of OC)), is greater than the outer surface hardness (H_(inner core surface)) of the inner core by at least 3 Shore C units and more preferably by at least 5 Shore C.

The core structure also has a hardness gradient across the entire core assembly. In one embodiment, the (H_(inner core center)) is in the range of about 10 Shore C to about 60 Shore C, preferably about 20 Shore C to about 50 Shore C; and the (H_(outer surface of OC)) is in the range of about 40 Shore C to about 90 Shore C, preferably about 43 Shore C to about 87 Shore C, to provide a positive hardness gradient across the core assembly. In another embodiment, the (H_(inner core center)) is in the range of about 10 Shore C to about 60 Shore C, preferably about 13 Shore C to about 55 Shore C; and the (H_(outer surface of OC)) is in the range of about 65 to about 96 Shore C, preferably about 68 Shore C to about 94 Shore C or about 75 Shore C to about 93 Shore C, to provide a positive hardness gradient across the core assembly. The gradient across the core assembly will vary based on several factors including, but not limited to, the dimensions of the inner core, intermediate core, and outer core layers.

As discussed above, the inner core is preferably formed from a foamed thermoplastic or thermoset composition and more preferably foamed polyurethanes. And, the outer core layer is formed preferably from a foamed or non-foamed thermoset composition or a foamed or non-foamed thermoplastic composition.

The inner core preferably has a diameter in the range of about 0.100 to about 1.100 inches, or a diameter of 1.30 inches or greater, or 1.40 inches or greater, or 1.50 inches or greater, or 1.60 inches or greater, or 1.70 inches or greater, or 1.80 inches or greater, or 1.90 inches or greater, or 2.00 inches or greater, or 2.10 or greater, or 2.20 or greater. For example, the inner core may have a diameter within a range of about 0.100 to about 0.500 inches. In another example, the inner core may have a diameter within a range of about 0.300 to about 0.800 inches. More particularly, the inner core may have a diameter size with a lower limit of about 0.10 or 0.12 or 0.15 or 0.25 or 0.30 or 0.35 or 0.45 or 0.55 inches and an upper limit of about 0.60 or 0.65 or 0.70 or 0.80 or 0.90 or 1.00 or 1.10 inches, or the inner core may have a diameter of 1.30 inches or greater, or 1.40 inches or greater, or 1.50 inches or greater, or 1.60 inches or greater, or 1.70 inches or greater, or 1.80 inches or greater, or 1.90 inches or greater, or 2.00 inches or greater, or 2.10 or greater, or 2.20 or greater. As far as the optional outer core layer is concerned, it preferably has a thickness in the range of about 0.100 to about 0.750 inches. For example, the lower limit of thickness may be about 0.050 or 0.100 or 0.150 or 0.200 or 0.250 or 0.300 or 0.340 or 0.400 and the upper limit may be about 0.500 or 0.550 or 0.600 or 0.650 or 0.700 or 0.750 inches.

Dual-layered core structures containing layers with various thickness and volume levels may be made in accordance with this invention. For example, in one version, the total diameter of the core structure is 0.20 inches and the total volume of the core structure is 0.23 cc. More particularly, in this example, the diameter of the inner core is 0.10 inches and the volume of the inner core is 0.10 cc; while the thickness of the outer core is 0.100 inches and the volume of the outer core is 0.13 cc. In another version, the total core diameter is about 1.55 inches and the total core volume is 31.96 cc. In this version, the outer core layer has a thickness of 0.400 inches and volume of 28.34 cc. Meanwhile, the inner core has a diameter of 0.75 inches and volume of 3.62 cm. In one embodiment, the volume of the outer core layer is greater than the volume of the inner core. In another embodiment, the volume of the outer core layer and inner core are equivalent. In still another embodiment, the volume of the outer core layer is less than the volume of the inner core.

Other examples of core structures containing layers of varying thicknesses and volumes are described below in Table 1C, wherein the inner core is foamed.

TABLE 1C Sample Core Dimensions Outer Foamed Total Total Core Outer Inner Volume Ex- Core Core Thick- Core Core of Inner ample Diameter Volume ness Volume Diameter Core A 0.30″  0.23 cc 0.100″  0.13 cc 0.10″  0.10 cc B 1.60″ 33.15 cc 0.750″ 33.05 cc 0.10″  0.10 cc C 1.55″ 31.96 cc 0.225″ 11.42 cc 1.10″ 11.42 cc D 1.55″ 31.96 cc 0.400″ 28.34 cc 0.75″  3.62 cc E 1.55″ 31.96 cc 0.525″ 28.34 cc 0.50″  3.62 cc

In one preferred embodiment, the inner core has a specific gravity in the range of about 0.25 to about 1.25 g/cc. Also, as discussed above, the specific gravity of the inner core may vary at different points of the inner core structure. That is, there may be a specific gravity gradient in the inner core. For example, in one preferred version, the geometric center of the inner core has a density in the range of about 0.25 to about 0.75 g/cc; while the outer skin of the inner core has a density in the range of about 0.75 to about 1.50 g/cc.

Meanwhile, the outer core layer preferably has a relatively high specific gravity. Thus, the specific gravity of the inner core layer (SG_(inner)) is preferably less than the specific gravity of the outer core layer (SG_(outer)). By the term, “specific gravity of the outer core layer” (“SG_(outer)”), it is generally meant the specific gravity of the outer core layer as measured at any point of the outer core layer. The specific gravity values at different points in the outer core layer may vary. That is, there may be specific gravity gradients in the outer core layer similar to the inner core. For example, the outer core layer may have a specific gravity within a range having a lower limit of about 0.50 or 0.60 or 0.70 or 0.75 or 0.85 or 0.90 or 0.95 or 1.00 or 1.10 or 1.25 or 1.30 or 1.36 or 1.40 or 1.42 or 1.48 or 1.50 or 1.60 or 1.66 or 1.75 or 2.00 and an upper limit of 2.50 or 2.60 or 2.80 or 2.90 or 3.00 or 3.10 or 3.25 or 3.50 or 3.60 or 3.80 or 4.00, 4.25 or 5.00 or 5.10 or 5.20 or 5.30 or 5.40 or 6.00 or 6.20 or 6.25 or 6.30 or 6.40 or 6.50 or 7.00 or 7.10 or 7.25 or 7.50 or 7.60 or 7.65 or 7.80 or 8.00 or 8.20 or 8.50 or 9.00 or 9.75 or 10.00 g/cc.

In general, the specific gravities of the respective pieces of an object affect the Moment of Inertia (MOI) of the object. The Moment of Inertia of a ball (or other object) about a given axis generally refers to how difficult it is to change the ball's angular motion about that axis. If the ball's mass is concentrated towards the center (the center piece (for example, inner core) has a higher specific gravity than the outer piece (for example, outer core layers), less force is required to change its rotational rate, and the ball has a relatively low Moment of Inertia. In such balls, most of the mass is located close to the ball's axis of rotation and less force is needed to generate spin. Thus, the ball has a generally high spin rate as the ball leaves the club's face after making impact. Conversely, if the ball's mass is concentrated towards the outer surface (the outer piece (for example, outer core layers) has a higher specific gravity than the center piece (for example, inner core), more force is required to change its rotational rate, and the ball has a relatively high Moment of Inertia. That is, in such balls, most of the mass is located away from the ball's axis of rotation and more force is needed to generate spin. Such balls have a generally low spin rate as the ball leaves the club's face after making impact.

More particularly, as described in Sullivan, U.S. Pat. No. 6,494,795 and Ladd et al., U.S. Pat. No. 7,651,415, the formula for the Moment of Inertia for a sphere through any diameter is given in the CRC Standard Mathematical Tables, 24th Edition, 1976 at 20 (hereinafter CRC reference). The term, “specific gravity” as used herein, has its ordinary and customary meaning, that is, the ratio of the density of a substance to the density of water at 4° C., and the density of water at this temperature is 1 g/cm³.

Embodiments are envisioned wherein at least one of the inner core and outer core layer is also foamed. In one embodiment, the inner core is made of a foamed composition helps provide a relatively low spin ball having good resiliency. The inner foam cores of this invention preferably have a Coefficient of Restitution (COR) of about 0.300 or greater; more preferably about 0.400 or greater, and even more preferably about 0.450 or greater. The resulting balls containing the dual-layered core constructions of this invention and cover of at least one layer preferably have a COR of about 0.700 or greater, more preferably about 0.730 or greater; and even more preferably about 0.750 to 0.810 or greater. The inner foam cores preferably have a Soft Center Deflection Index (“SCDI”) compression, as described in the Test Methods below, in the range of about 50 to about 190, and more preferably in the range of about 60 to about 170.

The USGA has established a maximum weight of 45.93 g (1.62 ounces) for golf balls. For play outside of USGA rules, the golf balls can be heavier. In one preferred embodiment, the weight of the multi-layered core is in the range of about 28 to about 38 grams. Also, golf balls made in accordance with this invention can be of any size, although the USGA requires that golf balls used in competition have a diameter of at least 1.68 inches. For play outside of United States Golf Association (USGA) rules, the golf balls can be of a smaller size. Normally, golf balls are manufactured in accordance with USGA requirements and have a diameter in the range of about 1.68 to about 1.80 inches. The present invention provides large diameter golf balls having an overall diameter of 1.70 inches or greater, or greater than 1.70 inches, or 1.80 inches or greater, or 1.90 inches or greater, or 2.00 inches or greater, or 2.10 inches or greater, or 2.20 inches or greater. As discussed further below, the golf ball contains a cover which may be multi-layered and in addition may contain intermediate (casing) layers, and the thickness levels of these layers also must be considered. Thus, in general, the dual-layer core structure normally has an overall diameter within a range having a lower limit of about 1.00 or 1.20 or 1.30 or 1.40 inches and an upper limit of about 1.58 or 1.60 or 1.62 or 1.66 inches, and more preferably in the range of about 1.3 to 1.65 inches. In one embodiment, the diameter of the core sub-assembly is in the range of about 1.45 to about 1.62 inches.

Cover Structure

The golf ball of this invention may be enclosed with one or more cover layers disposed about the foamed intermediate layer. In one particularly preferred version, the golf ball includes a multi-layered cover comprising inner and outer cover layers. The inner cover layer is preferably formed from a composition comprising an ionomer or a blend of two or more ionomers that helps impart hardness to the ball. In a particular embodiment, the inner cover layer is formed from a composition comprising a high acid ionomer. A particularly suitable high acid ionomer is Surlyn 8150® (DuPont). Surlyn 8150® is a copolymer of ethylene and methacrylic acid, having an acid content of 19 wt %, which is 45% neutralized with sodium. In another particular embodiment, the inner cover layer is formed from a composition comprising a high acid ionomer and a maleic anhydride-grafted non-ionomeric polymer. A particularly suitable maleic anhydride-grafted polymer is Fusabond 525D® (DuPont). Fusabond 525D® is a maleic anhydride-grafted, metallocene-catalyzed ethylene-butene copolymer having about 0.9 wt % maleic anhydride grafted onto the copolymer. A particularly preferred blend of high acid ionomer and maleic anhydride-grafted polymer is an 84 wt %/16 wt % blend of Surlyn 8150® and Fusabond 525D®. Blends of high acid ionomers with maleic anhydride-grafted polymers are further disclosed, for example, in U.S. Pat. Nos. 6,992,135 and 6,677,401, the entire disclosures of which are hereby incorporated herein by reference.

The inner cover layer also may be formed from a composition comprising a 50/45/5 blend of Surlyn® 8940/Surlyn® 9650/Nucrel® 960, and, in a particularly preferred embodiment, the composition has a material hardness of from 80 to 85 Shore C. In yet another version, the inner cover layer is formed from a composition comprising a 50/25/25 blend of Surlyn® 8940/Surlyn® 9650/Surlyn® 9910, preferably having a material hardness of about 90 Shore C. The inner cover layer also may be formed from a composition comprising a 50/50 blend of Surlyn® 8940/Surlyn® 9650, preferably having a material hardness of about 86 Shore C. A composition comprising a 50/50 blend of Surlyn® 8940 and Surlyn® 7940 also may be used. Surlyn® 8940 is an E/MAA copolymer in which the MAA acid groups have been partially neutralized with sodium ions. Surlyn® 9650 and Surlyn® 9910 are two different grades of E/MAA copolymer in which the MAA acid groups have been partially neutralized with zinc ions. Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt % methacrylic acid.

A wide variety of materials may be used for forming the outer cover including, for example, polyurethanes; polyureas; copolymers, blends and hybrids of polyurethane and polyurea; olefin-based copolymer ionomer resins (for example, Surlyn® ionomer resins and DuPont HPF® 1000 and HPF® 2000, commercially available from DuPont; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylic acid copolymers, commercially available from The Dow Chemical Company; and Clarix® ionomer resins, commercially available from A. Schulman Inc.); polyethylene, including, for example, low density polyethylene, linear low density polyethylene, and high density polyethylene; polypropylene; rubber-toughened olefin polymers; acid copolymers, for example, poly(meth)acrylic acid, which do not become part of an ionomeric copolymer; plastomers; flexomers; styrene/butadiene/styrene block copolymers; styrene/ethylene-butylene/styrene block copolymers; dynamically vulcanized elastomers; copolymers of ethylene and vinyl acetates; copolymers of ethylene and methyl acrylates; polyvinyl chloride resins; polyamides, poly(amide-ester) elastomers, and graft copolymers of ionomer and polyamide including, for example, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc; cross-linked trans-polyisoprene and blends thereof; polyester-based thermoplastic elastomers, such as Hytrel®, commercially available from DuPont or RiteFlex®, commercially available from Ticona Engineering Polymers; polyurethane-based thermoplastic elastomers, such as Elastollan®, commercially available from BASF; synthetic or natural vulcanized rubber; and combinations thereof. Castable polyurethanes, polyureas, and hybrids of polyurethanes-polyureas are particularly desirable because these materials can be used to make a golf ball having high resiliency and a soft feel. By the term, “hybrids of polyurethane and polyurea,” it is meant to include copolymers and blends thereof.

Polyurethanes, polyureas, and blends, copolymers, and hybrids of polyurethane/polyurea are also particularly suitable for forming cover layers. When used as cover layer materials, polyurethanes and polyureas can be thermoset or thermoplastic. Thermoset materials can be formed into golf ball layers by conventional casting or reaction injection molding techniques. Thermoplastic materials can be formed into golf ball layers by conventional compression or injection molding techniques.

The compositions used to make the casing (mantle) and cover layers may contain a wide variety of fillers and additives to impart specific properties to the ball. For example, relatively heavy-weight and light-weight metal fillers such as, particulate; powders; flakes; and fibers of copper, steel, brass, tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, and platinum, and alloys and combinations thereof may be used to adjust the specific gravity of the ball. Other additives and fillers include, but are not limited to, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, surfactants, processing aids, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, titanium dioxide, clay, mica, talc, glass flakes, milled glass, and mixtures thereof.

The inner cover layer preferably has a material hardness within a range having a lower limit of 70 or 75 or 80 or 82 Shore C and an upper limit of 85 or 86 or 90 or 92 Shore C. The thickness of the intermediate layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.045 or 0.080 or 0.120 inches. The outer cover layer preferably has a material hardness of 85 Shore C or less. The thickness of the outer cover layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.055 or 0.080 inches. Methods for measuring hardness of the layers in the golf ball are described in further detail below.

A single cover or, preferably, an inner cover layer is formed around the outer core layer. When an inner cover layer is present, an outer cover layer is formed over the inner cover layer. Most preferably, the inner cover is formed from an ionomeric material and the outer cover layer is formed from a polyurethane material, and the outer cover layer has a hardness that is less than that of the inner cover layer. Preferably, the inner cover has a hardness of greater than about 60 Shore D and the outer cover layer has a hardness of less than about 60 Shore D. In an alternative embodiment, the inner cover layer is comprised of a partially or fully neutralized ionomer, a thermoplastic polyester elastomer such as Hytrel™, commercially available form DuPont, a thermoplastic polyether block amide, such as Pebax™, commercially available from Arkema, Inc., or a thermoplastic or thermosetting polyurethane or polyurea, and the outer cover layer is comprised of an ionomeric material. In this alternative embodiment, the inner cover layer has a hardness of less than about 60 Shore D and the outer cover layer has a hardness of greater than about 55 Shore D and the inner cover layer hardness is less than the outer cover layer hardness.

In one embodiment, a multi-layered cover comprising inner and outer cover layers is formed, where the inner cover layer has a thickness of about 0.01 inches to about 0.06 inches, more preferably about 0.015 inches to about 0.040 inches, and most preferably about 0.02 inches to about 0.035 inches. In this version, the inner cover layer is formed from a partially- or fully-neutralized ionomer having a Shore D hardness of greater than about 55, more preferably greater than about 60, and most preferably greater than about 65. The outer cover layer, in this embodiment, preferably has a thickness of about 0.015 inches to about 0.055 inches, more preferably about 0.02 inches to about 0.04 inches, and most preferably about 0.025 inches to about 0.035 inches, with a hardness of about Shore D 80 or less, more preferably 70 or less, and most preferably about 60 or less. The inner cover layer is harder than the outer cover layer in this version. A preferred outer cover layer is a castable or reaction injection molded polyurethane, polyurea or copolymer, blend, or hybrid thereof having a Shore D hardness of about 40 to about 50. In another multi-layer cover, dual-core embodiment, the outer cover and inner cover layer materials and thickness are the same but, the hardness range is reversed, that is, the outer cover layer is harder than the inner cover layer. For this harder outer cover/softer inner cover embodiment, the ionomer resins described above would preferably be used as outer cover material.

Manufacturing of Golf Balls

As described above, the foamed intermediate layer is preferably is formed by a casting method. Compression or injection molding techniques may be used to form the other layers of the golf ball. Surface-treatments may ne used as desired to increase the adhesion between an outer surface of one layer and the next layer. Such surface-treatment may include mechanically or chemically-abrading the outer surface of the core. Other examples include corona-discharge, plasma-treatment, silane-dipping, or other treatment methods known to those in the art.

The cover layers are formed over the core or ball sub-assembly (the core structure and any casing layers disposed about the core) using a suitable technique such as, for example, compression-molding, flip-molding, injection-molding, retractable pin injection-molding, reaction injection-molding (RIM), liquid injection-molding, casting, spraying, powder-coating, vacuum-forming, flow-coating, dipping, spin-coating, and the like. Preferably, each cover layer is separately formed over the ball subassembly. For example, an ethylene acid copolymer ionomer composition may be injection-molded to produce half-shells. Alternatively, the ionomer composition can be placed into a compression mold and molded under sufficient pressure, temperature, and time to produce the hemispherical shells. The smooth-surfaced hemispherical shells are then placed around the core sub-assembly in a compression mold. Under sufficient heating and pressure, the shells fuse together to form an inner cover layer that surrounds the sub-assembly. In another method, the ionomer composition is injection-molded directly onto the core sub-assembly using retractable pin injection molding. An outer cover layer comprising a polyurethane or polyurea composition over the ball sub-assembly may be formed by using a casting process.

After the golf balls have been removed from the mold, they may be subjected to finishing steps such as flash-trimming, surface-treatment, marking, coating, and the like using techniques known in the art. For example, in traditional white-colored golf balls, the white-pigmented cover may be surface-treated using a suitable method such as, for example, corona, plasma, or ultraviolet (UV) light-treatment. Then, indicia such as trademarks, symbols, logos, letters, and the like may be printed on the ball's cover using pad-printing, ink-jet printing, dye-sublimation, or other suitable printing methods. Clear surface coatings (for example, primer and top-coats), which may contain a fluorescent whitening agent, are applied to the cover. The resulting golf ball has a glossy and durable surface finish.

In another finishing process, the golf balls are painted with one or more paint coatings. For example, white primer paint may be applied first to the surface of the ball and then a white top-coat of paint may be applied over the primer. Of course, the golf ball may be painted with other colors, for example, red, blue, orange, and yellow. As noted above, markings such as trademarks and logos may be applied to the painted cover of the golf ball. Finally, a clear surface coating may be applied to the cover to provide a shiny appearance and protect any logos and other markings printed on the ball.

Golf balls of the present invention typically have a dimple coverage of 50% or greater, or 60% or greater, or 65% or greater, or 70% or greater, or 75% or greater, or 80% or greater, or 85% or greater, or 90% or greater, or 95% or greater.

The dimples are not limited to a particular plan view shape, and, in one embodiment, have a plan view shape selected from circular, polygonal, oval, flower-like lobed shape, multi-armed shape, amorphous shape, and annular shape.

The dimples are not limited to a particular cross-sectional profile shape, and, in one embodiment, have a profile shape selected from spherical, truncated, catenary, multi-radius, saucer, dimple-in-dimple, conical, and bramble.

The dimples are not limited to a particular dimple arrangement, and, in one embodiment, are arranged in an overall pattern selected from polyhedron-based patterns (e.g., icosahedron, octahedron, dodecahedron, icosidodecahedron, cuboctahedron, and triangular dipyramid), phyllotaxis-based patterns, spherical tiling patterns, and random arrangements.

In a particular embodiment, the dimples have a diameter of from 6% to 12% of the ball diameter and a surface depth, as measured from the phantom ball surface over the dimple to the bottom of the dimple, of from 0.3% to 1.0% of the ball diameter. In a particular aspect of this embodiment, the dimples have an edge angle of from 13° to 20°. In another particular aspect of this embodiment, the total dimple volume, defined herein as the space enclosed between the phantom ball surface and the actual ball surface, is from 1.0% to 2.0% of the phantom ball volume. In another particular aspect of this embodiment, the dimple count is from 300 to 500. In another particular aspect of this embodiment, the ball has a diameter of from 1.68 inches to 2.00 inches.

In another particular embodiment, the dimples have a diameter of from 3% to 14% of the ball diameter, or from 3% to 9% of the ball diameter, and a surface depth, as measured from the phantom ball surface over the dimple to the bottom of the dimple, of from 0.2% to 1.5% of the ball diameter. In a particular aspect of this embodiment, the dimples have an edge angle of from 10° to 25°. In another particular aspect of this embodiment, the total dimple volume, defined herein as the space enclosed between the phantom ball surface and the actual ball surface, is from 0.5% to 3.0% of the phantom ball volume. In another particular aspect of this embodiment, the dimple count is from 300 to 700, or from 500 to 700. In another particular aspect of this embodiment, the ball has a diameter of from 2.00 inches or greater.

Generally, it may be difficult to define and measure the edge angle and diameter of a dimple due to the indistinct nature of the boundary dividing the undimpled land surface of the ball from the dimple depression. For example, the effects of paint and/or the dimple design itself can cause the junction between the land surface and the dimple sidewall to be indistinct, making the measurement of dimple edge angle and dimple diameter seem somewhat ambiguous. Thus, the following method can be used to define and measure edge angle and dimple diameter. A continuation of the land surface is constructed above the dimple to define the phantom surface of the ball. A first tangent line, T1, is then constructed at a point on the dimple sidewall that is spaced 0.003 inches radially inward from the phantom surface. T1 intersects the phantom surface at point P1, which defines a nominal dimple edge position. A second tangent line, T2, tangent to the phantom surface at P1, is then constructed. The edge angle is defined as the angle between T1 and T2. The dimple diameter is defined as the distance between P1 and the equivalent point diametrically opposite along the dimple perimeter. Alternatively, the dimple diameter is defined as twice the distance between P1 and the centerline, measured in a direction perpendicular to the centerline. Methods for defining and measuring dimple parameters are further disclosed, for example, in U.S. Pat. No. 6,916,255 to Aoyama et al. and U.S. Pat. No. 8,333,669 to Sullivan et al., the entire disclosures of which are hereby incorporated herein by reference.

Golf Balls Having Reduced-Distance

More particularly, in yet other embodiments of this invention, the above-described compositions can be used to make golf balls having reduced distance while performing similar to traditional high performance balls in other ways. That is, in these embodiments, the golf ball has high playing performance properties such as flight trajectory, spin rate, and feel, except the ball plays a shorter distance than traditional high performance balls.

For example, in one preferred embodiment, golf ball constructions as described in Sullivan et al., U.S. Pat. No. 8,152,656 (the '656 Patent), the disclosure of which is hereby incorporated by reference, can be made. Such a ball preferably has a weight from 1.30 to 1.620 ounces, a diameter from 1.670 to 1.800 inches, and a maximum Coefficient of Restitution (CoR) from about 0.500 to about 0.790 as measured at 125 ft/sec incoming ball velocity. More preferably the ball has a weight of from about 1.50 ounces to 1.60 ounces, a diameter of 1.680 to 1.720, inches, and a CoR of from about 0.625 to 0.775 as measured at 125 ft/sec incoming ball velocity. The ball has a drag to weight ratio of greater than 2.4 at a Reynolds number of about 207,000 and a spin ratio of about 0.095.

The '656 Patent also describes the reduced distance golf ball as having a relatively high coefficient of drag (C_(D)). In one embodiment, the C_(D) is greater than 0.26 at a Reynolds number of 150000 and a spin rate of 3000 RPM, and greater than 0.29 at a Reynolds number of 120000 and a spin rate of 3000 RPM. Further, golf balls prepared according to the present invention may have a relatively high coefficient of lift (C_(L)). In one embodiment, the C_(L) is greater than 0.21 at a Reynolds number of 150000 and a spin rate of 3000 RPM, and greater than 0.23 at a Reynolds number of 120000 and a spin rate of 3000 RPM.

In one embodiment, the golf ball has reduced flight distance while retaining the appearance of a normal trajectory that can be defined by two non-dimensional parameters that account for the lift, drag, size and weight of the ball. The coefficients are defined in in the following Equations: i) C_(D/W)=F_(D/W), and ii) C_(Lw)=F_(L/W).

A reduction in flight distance is attainable when a golf ball's size, weight, dimple pattern and dimple profiles are selected to satisfy specific C_(D/W) and C_(L/W) criteria at specified combinations of Reynolds number and spin ratios (or spin rate), and the only other remaining variable is the COR. The size of the golf ball affects the lift and drag of the ball, since these forces are directly proportional to the surface area of the ball. The weight of the ball makes up the denominator of coefficients C_(D/W) and C_(u w). Dimple patterns, for example, percentage of dimple coverage and geodesic patterns, can increase or decrease aerodynamic efficiency. Dimple profiles, e.g., edge angle, entry angle and shape (circular, polygonal), can increase or decrease the lift and/or drag experienced by the ball. According to the present invention, these factors can be selected or combined to yield desired C_(D/W) and/or C_(L/W) for a reduced distance golf ball that retains the appearance of a high performance trajectory.

Test Methods

Hardness.

The center hardness of a core is obtained according to the following procedure. The core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed. The core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result. The core is secured such that the parting line of the core is roughly parallel to the top of the holder. The diameter of the core is measured 90 degrees to this orientation prior to securing. A measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations. A rough cut is made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool, making sure that the core does not move in the holder during this step. The remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine. The exposed ‘rough’ surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height from the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within 0.004 inches. Leaving the core in the holder, the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark according to ASTM D-2240. Additional hardness measurements at any distance from the center of the core can then be made by drawing a line radially outward from the center mark, and measuring the hardness at any given distance along the line, typically in 2 mm increments from the center. The hardness at a particular distance from the center should be measured along at least two, preferably four, radial arms located 180° apart, or 90° apart, respectively, and then averaged. All hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder, and thus also parallel to the properly aligned foot of the durometer.

The outer surface hardness of a golf ball layer is measured on the actual outer surface of the layer and is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects, such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface, care must be taken to ensure that the golf ball or golf ball sub-assembly is centered under the durometer indenter before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for the hardness measurements. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand. The weight on the durometer and attack rate conforms to ASTM D-2240.

In certain embodiments, a point or plurality of points measured along the “positive” or “negative” gradients may be above or below a line fit through the gradient and its outermost and innermost hardness values. In an alternative preferred embodiment, the hardest point along a particular steep “positive” or “negative” gradient may be higher than the value at the innermost portion of the inner core (the geometric center) or outer core layer (the inner surface)—as long as the outermost point (i.e., the outer surface of the inner core) is greater than (for “positive”) or lower than (for “negative”) the innermost point (i.e., the geometric center of the inner core or the inner surface of the outer core layer), such that the “positive” and “negative” gradients remain intact.

As discussed above, the direction of the hardness gradient of a golf ball layer is defined by the difference in hardness measurements taken at the outer and inner surfaces of a particular layer. The center hardness of an inner core and hardness of the outer surface of an inner core in a single-core ball or outer core layer are readily determined according to the test procedures provided above. The outer surface of the inner core layer (or other optional intermediate core layers) in a dual-core ball are also readily determined according to the procedures given herein for measuring the outer surface hardness of a golf ball layer, if the measurement is made prior to surrounding the layer with an additional core layer. Once an additional core layer surrounds a layer of interest, the hardness of the inner and outer surfaces of any inner or intermediate layers can be difficult to determine. Therefore, for purposes of the present invention, when the hardness of the inner or outer surface of a core layer is needed after the inner layer has been surrounded with another core layer, the test procedure described above for measuring a point located 1 mm from an interface is used.

Also, it should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” For purposes of the present invention, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Surface hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. The difference in “surface hardness” and “material hardness” values is due to several factors including, but not limited to, ball construction (that is, core type, number of cores and/or cover layers, and the like); ball (or sphere) diameter; and the material composition of adjacent layers. It also should be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other. Shore hardness (for example, Shore C or Shore D hardness) was measured according to the test method ASTM D-2240.

Compression.

As disclosed in Jeff Dalton's Compression by Any Other Name, Science and Golf IV, Proceedings of the World Scientific Congress of Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), several different methods can be used to measure compression, including Atti compression, Riehle compression, load/deflection measurements at a variety of fixed loads and offsets, and effective modulus. For purposes of the present invention, compression refers to Soft Center Deflection Index (“SCDI”). The SCDI is a program change for the Dynamic Compression Machine (“DCM”) that allows determination of the pounds required to deflect a core 10% of its diameter. The DCM is an apparatus that applies a load to a core or ball and measures the number of inches the core or ball is deflected at measured loads. A crude load/deflection curve is generated that is fit to the Atti compression scale that results in a number being generated that represents an Atti compression. The DCM does this via a load cell attached to the bottom of a hydraulic cylinder that is triggered pneumatically at a fixed rate (typically about 1.0 ft/s) towards a stationary core. Attached to the cylinder is an LVDT that measures the distance the cylinder travels during the testing timeframe. A software-based logarithmic algorithm ensures that measurements are not taken until at least five successive increases in load are detected during the initial phase of the test. The SCDI is a slight variation of this set up. The hardware is the same, but the software and output has changed. With the SCDI, the interest is in the pounds of force required to deflect a core x amount of inches. That amount of deflection is 10% percent of the core diameter. The DCM is triggered, the cylinder deflects the core by 10% of its diameter, and the DCM reports back the pounds of force required (as measured from the attached load cell) to deflect the core by that amount. The value displayed is a single number in units of pounds.

Drop Rebound. By “drop rebound,” it is meant the number of inches a sphere will rebound when dropped from a height of 72 inches in this case, measuring from the bottom of the sphere. A scale, in inches is mounted directly behind the path of the dropped sphere and the sphere is dropped onto a heavy, hard base such as a slab of marble or granite (typically about 1 ft wide by 1 ft high by 1 ft deep). The test is carried out at about 72-75° F. and about 50% RH.

Coefficient of Restitution (“COR”).

The COR is determined according to a known procedure, wherein a golf ball or golf ball sub-assembly (for example, a golf ball core) is fired from an air cannon at two given velocities and a velocity of 125 ft/s is used for the calculations. Ballistic light screens are located between the air cannon and steel plate at a fixed distance to measure ball velocity. As the ball travels toward the steel plate, it activates each light screen and the ball's time period at each light screen is measured. This provides an incoming transit time period which is inversely proportional to the ball's incoming velocity. The ball makes impact with the steel plate and rebounds so it passes again through the light screens. As the rebounding ball activates each light screen, the ball's time period at each screen is measured. This provides an outgoing transit time period which is inversely proportional to the ball's outgoing velocity. The COR is then calculated as the ratio of the ball's outgoing transit time period to the ball's incoming transit time period (COR=V_(out)/V_(in)=T_(in)/T_(out)).

Density.

The density refers to the weight per unit volume (typically, g/cm³) of the material and can be measured per ASTM D-1622. Density is also defined in units g/cc and the terms density and specific gravity are used herein interchangeably.

The present invention is illustrated further by the following Examples, but these Examples should not be construed as limiting the scope of the invention.

Examples

The examples below are for illustrative purposes only. In no manner is the present invention limited to the specific disclosures therein.

In the following Examples, different foam formulations were used to prepare core samples and may be used to prepare foam intermediate layers (or cores/subassemblies) using the above-described molding methods. The different formulations are described in Tables 2 and 3 below.

TABLE 2 (Sample A) Ingredient Weight Percent 4,4 Methylene Diphenyl Diisocyanate (MDI) 14.65% Polyetratmethylene ether glycol (PTMEG 2000) 34.92% *Mondur ™ 582 (2.5 fn) 29.11% Trifunctional caprolactone polyol (CAPA 3031) (3.0 fn) 20.22% Water 0.67% **Niax ™ L-1500 surfactant 0.04% *** KKAT ™ XK 614 catalyst 0.40% Dibutyl tin dilaurate (T-12) 0.03% *Mondur ™ 582 (2.5 fn) - polymeric methylene diphenyl diisocyanate (p-MDI) with 2.5 functionality, available from Bayer Material Science. **Niax ™ L-1500 silicone-based surfactant, available from Momentive Specialty Chemicals, Inc. *** KKAT ™ XK 614 zinc-based catalyst, available from King Industries.

The resulting spherical core Sample A (0.75 inch diameter) had a density of 0.45 g/cm³, a compression (SCDI) of 75, and drop rebound of 46% based on average measurements using the test methods as described above.

TABLE 3 (Sample B) Ingredient Weight Percent Mondur ™ 582 (2.5 fn) 30.35% *Desmodur ™ 3900 aliphatic 30.35% **Polymeg ™ 650 19.43% ***Ethacure ™ 300 19.43% Water 0.31% Niax ™ L-1500 surfactant 0.04% Dibutyl tin dilaurate (T-12) 0.09% *Desmodur ™ 3900 - polyfunctional aliphatic polyisocyanate resin based on hexamethylene diisocyanate (HDI), available from Bayer Material Science. **Polymeg ™ 650 - polyetratmethylene ether glycol, available from Lyondell Chemical Company. ***Ethacure ™ 300 - aromatic diamine curing agent, available from Albemarle Corp.

The resulting spherical core Sample B (0.75 inch diameter) had a density of 0.61 g/cm³, a compression (SCDI) of 160, and drop rebound of 56% based on average measurements using the test methods as described above.

In the following Examples, different foam formulations were used to prepare single core samples using the above-described molding methods and may be used to prepare foam intermediate layers as well. The different formulations are described in Tables 4-8 below. The resulting spherical cores were measured for density and tested for compression and Coefficient of Restitution (COR) using the test methods as described above and the results are reported in Tables 4-8.

Concentrations are in parts per hundred (phr) unless otherwise indicated. As used herein, the term “parts per hundred,” also known as “phr,” is defined as the number of parts by weight of a particular component present in a mixture, relative to 100 parts by weight of the base rubber component. Mathematically, this can be expressed as the weight of an ingredient divided by the total weight of the polymer, multiplied by a factor of 100.

TABLE 4 Spherical Foam Core Samples Example No. 1 2 3 4 5 6 6.5% MDI 41 43.72 45.01 33.58 49.48 31.83 Prepolymer Mondur MR 7.33 13.64 Mondur CD 19.75 Mondur ML 17 13.06 8.06 Poly THF 650 22.2 13.06 29.01 CAPA 3031 13.77 13.77 4 CAPA 3091 27.86 CAPA 4101 CAPA 4801 D.I. Water 0.5 0.50 0.45 0.50 0.45 0.50 Niax 1500 0.75 0.75 0.75 0.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 Garamite 1958 0.375 0.375 0.375 0.375 0.375 Total Parts 76.345 76.315 76.315 76.325 75.05 76.305 Density 0.54 0.7 0.6 0.53 0.6 Compression 35 106 −217 −242 −217 CoR @125 ft/s 0.434 0.503 0.52 0.278 0.41 6.5% MDI Prepolymer is made from 4,4′-MDI and polytetramethylene glycol ether Mondur ™ MR—polymeric MDI, available from Bayer. Mondur ™ CD—modified 4,4′-MDI, available from Bayer. Mondur ™ ML—isomer mixture of 2,4 and 4,4′-MDI, available from Bayer. Poly THF ™ 650—650 molecular weight polyetratmethylene ether glycol (PTMEG), available from BASF. CAPA ™ 3031—low molecular weight trifunctional polycaprolactone polyol, available from Perstorp CAPA ™ 3091—polyester triol terminated by primary hydroxyl groups, available from Perstorp. CAPA ™ 4101—tetra-functional polyol terminated with primary hydroxyl groups, available from Perstorp. CAPA ™ 4801—tetra-functional polyol terminated with primary hydroxyl groups, available from Perstorp. Niax ™ L-1500—silicone surfactant from Momentive Specialty Chemicals, Inc. Vanox ™ MBPC—antioxidant, available from R.T. Vanderbuilt. Irganox ™ 1135—antioxidant, available BASF. Dabco ™ 33LV—tertiary amine catalyst, available from Air Products. Garamite ™ 1958—rheological additive, available from Southern Clay.

TABLE 5 Spherical Foam Core Samples Example No. 7 8 9 10 11 12 6.5% MDI Prepolymer 21.67 45.81 49.22 45.01 45.01 55.8 Mondur MR 18.46 7.46 8.01 7.33 7.33 9.08 Mondur CD Mondur ML Poly THF 650 34.33 20.57 13 22.2 22.2 CAPA 3031 0.7 4 9.66 CAPA 3091 CAPA 4101 CAPA 4801 D.I. Water 0.53 0.45 0.45 0.45 0.45 0.45 Niax 1500 0.75 0.75 0.75 0.75 0.75 0.75 Varox MPBC 0.375 Irganox 1135 0.38 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 0.2 Garamite 1958 0.375 0.375 0.375 0.375 0.375 0.375 Total Parts 76.315 76.315 76.005 76.69 76.695 76.315 Density 0.46 0.4 Compression −245 −109 CoR @125 ft/s 0.388 0.515

TABLE 6 Spherical Foam Core Samples Example No. 13 14 15 16 17 18 6.5% MDI 68.81 44.28 33.1 42.39 49.48 40.75 Prepolymer Mondur MR 12.49 17.05 11.96 8.06 11.5 Mondur CD Mondur ML Poly THF 650 CAPA 3031 5.79 5.047 2.86 2.37 2 CAPA 3091 CAPA 4101 12.67 21.48 17.79 15 22.27 CAPA 4801 D.I. Water 0.39 0.45 0.67 0.48 0.45 0.48 Niax 1500 0.75 0.75 0.75 0.75 0.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 0.2 0.2 Garamite 1958 0.375 0.375 0.38 0.38 0.38 0.38 Total Parts 76.315 76.262 76.49 76.32 76.32 76.33 Density 0.52 0.35 0.64 0.39 0.46 0.39 Compression −200 −144 45 −135 −165 −120 CoR @125 ft/s 0.54 0.534 0.571 0.553 0.537 0.543

TABLE 7 Spherical Foam Core Samples Example No. 19 20 21 22 6.5% MDI Prepolymer 47.83 56.05 29.18 19.58 Mondur MR 7.78 9.12 12.51 16.68 Mondur CD Mondur ML Poly THF 650 CAPA 3031 CAPA 3091 CAPA 4101 18.92 18.11 17.37 20.23 CAPA 4801 16.1 15.44 17.98 D.I. Water 0.45 0.61 0.5 0.52 Niax 1500 0.75 0.75 0.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 Garamite 1958 0.38 0.38 0.38 0.38 Total Parts 76.31 101.32 76.33 76.32 Density 0.42 0.66 0.51 Compression −165 −169 −100 CoR @125 ft/s 0.609 0.492 0.425

TABLE 8 Spherical Foam Core Samples Example No. 23 24 25 26 6.5% MDI Prepolymer 43.87 50.63 37.21 43.57 Mondur MR 9.63 5.63 13.07 9.56 Mondur CD Mondur ML Poly THF 650 CAPA 3031 CAPA 3091 CAPA 4101 18.36 15.98 21.18 16.15 CAPA 4801 D.I. Water 0.47 0.45 0.49 0.47 Niax 1500 0.75 0.75 0.75 0.75 Varox MPBC Irganox 1135 Dabco 33LV 0.2 0.2 0.2 0.2 Garamite 1958 0.38 0.38 0.38 0.38 Total Parts 76.31 76.33 76.34 76.33 Density 0.46 0.57 0.43 0.48 Compression −164 −169 −137 −147 CoR @125 ft/s 0.578 0.600 0.541 0.571

In the following Examples, different formulations were used to prepare dual-core samples having a foam center and surrounding thermoset outer core layer using the above-described molding methods. The sample cores were tested for compression (DCM), Coefficient of Restitution (COR), and hardness using the above-described test methods and the results are reported below in Table 13.

Concentrations are in parts per hundred (phr) unless otherwise indicated. As used herein, the term “parts per hundred,” also known as “phr,” is defined as the number of parts by weight of a particular component present in a mixture, relative to 100 parts by weight of the base rubber component. Mathematically, this can be expressed as the weight of an ingredient divided by the total weight of the polymer, multiplied by a factor of 100.

Sample C (0.5″ foamed center) In this Sample, the foam formulation in below Table 9 was used to prepare an inner core having a diameter of 0.5 inches.

TABLE 9 (Foam Center of Sample C) Ingredient Parts 6.5% MDI Prepolymer 45.010 Mondur ™ 582 (2.5 fn) 7.330 Poly THF ™ 650 22.200 Deionized Water 0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 1958 0.375

The following rubber formulation (Table 10) was molded about the foamed inner core and cured to form a thermoset rubber outer core layer.

TABLE 10 (Rubber Outer Core Layer of Sample C) Ingredient Parts *Buna ™ CB23 100.0 Zinc Diacrylate (ZDA) 35.0 **Perkadox BC 0.5 Zinc Pentachlorothiophenol (ZnPCTP) 0.5 Zinc Oxide 14.9 *Buna ™ CB23 - polybutadiene rubber, available from Lanxess Corp. **Perkadox ™ BC, peroxide free-radical initiator, available from Akzo Nobel.

The dual-layered core of Sample C (foam center and thermoset rubber outer core layer with a center diameter of 0.5) inches was tested for hardness and the core was found to have a hardness gradient (across the entire core as measured at points in millimeters (mm) from the geometric center) in the range of about 21 Shore C to about 89 Shore C. The hardness of the core measured at the geometric center was about 21 Shore C and the hardness of the core measured at about 20 mm from the geometric center (that is, the surface of the outer core layer) was about 89 Shore C. The hardness values measured at various points along this core structure are described in Table 17 below and the hardness plot is shown in FIG. 5.

Sample D (0.5″ Foamed Center)

In this Sample D, the foam formulation in below Table 11 was used to prepare an inner core having a diameter of 0.5 inches.

TABLE 11 (Foam Center of Sample D) Ingredient Parts 6.5% MDI Prepolymer 55.800 Mondur ™ 582 (2.5 fn) 9.080 CAPA ™ 3031 9.660 Deionized Water 0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 1958 0.375

The same rubber formulation as described above in Sample C (Table 10) was molded about the foam center of Sample D and cured to form a thermoset rubber outer core layer.

Sample E (0.5″ Foamed Center)

In this Sample E, the foam formulation in below Table 12 was used to prepare an inner core having a diameter of 0.5 inches.

TABLE 12 (Foam Center of Sample E) Ingredient Parts 6.5% MDI Prepolymer 44.280 Mondur ™ 582 (2.5 fn) 12.490 CAPA ™ 3031 5.047 Deionized Water 0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 1958 0.375

The same rubber formulation as described above in Sample C (Table 10) was molded about the foam center of Sample E and cured to form a thermoset rubber outer core layer.

TABLE 13 Properties of Core Samples (C-E) Compression COR@125 Surface Center Hardness Sample (DCM) ft/sec Hardness Hardness Gradient C 85 0.816 88.9 22.1 66.8 D 81 0.797 86.1 46.0 40.2 E 81 0.806 87.0 43.7 43.3

Sample F (0.75″ Foamed Center)

In this Sample, the foam formulation in below Table 14 was used to prepare an inner core having a diameter of 0.75 inches.

TABLE 14 (Foam Center of Sample F) Ingredient Parts 6.5% MDI Prepolymer 47.830 Mondur ™ 582 (2.5 fn) 7.780 CAPA ™ 4101 18.920 Deionized Water 0.450 Niax ™ L-1500 surfactant 0.750 Dabco ™ 33LV 0.200 Garamite ™ 1958 0.380

In this Sample F, the following rubber formulation (Table 15) was molded about the foamed inner core and cured to form a thermoset rubber outer core layer. Different core samples having different densities (F1-F5) were prepared and are further described in Table 17 below.

TABLE 15 (Rubber Outer Core Layer of Sample F) Ingredient Parts Buna ™ CB23 100.0 Zinc Diacrylate (ZDA) 36.0 Perkadox BC 0.5 Zinc Pentachlorothiophenol (ZnPCTP) 0.5 Zinc Oxide 21.3

The Sample F1-F5 cores were tested for compression (DCM), Coefficient of Restitution (COR), and hardness using the above-described test methods and the results are reported below in Table 16.

TABLE 16 Properties of Core Samples (F1-F5) Density of Foamed Surface Center Hardness Center Compression Hardness Hardness Gradient Sample (g/cm³) (DCM) COR@125 ft/sec (Shore C) (Shore C) (Shore C) F-1 0.40 80 0.779 86.6 33.5 53.0 F-2 0.46 78 0.775 86.4 31.8 54.3 F-3 0.59 77 0.770 86.4 34. 52.3 F-4 0.75 78 0.769 87.3 43.0 44.3 F-5 0.83 75 0.766 87.4 37.4 50.0

The dual-layered core of Sample F-2 (foam center and thermoset rubber outer core layer having a center diameter of 0.75 inches) was tested for hardness and the core was found to have a hardness gradient (across the entire core as measured at points in millimeters (mm) from the geometric center) in the range of about 32 Shore C to about 86 Shore C. The hardness of the core measured at the geometric center was about 32 Shore C and the hardness of the core measured at about 20 mm from the geometric center (that is, the surface of the outer core layer) was about 86 Shore C. The hardness values measured at various points along the core structure are described in Table 17 below and the hardness plot is shown in FIG. 5.

TABLE 17 Hardness Properties of Core Samples (C and F-2) Distance from Geometric Center Hardness Gradient of Hardness Gradient of of Core Sample (mm) Sample C (Shore C) Sample F-2 (Shore C)  0 (Center) 21 31.8 2 20.8 32.6 4 25 35.7 6 28.1 35.1 8 72 37.8 10 72.8 70.9 12 73.1 70.2 14 72.7 70.2 16 76.5 76.9 18 82.6 81.8 20 (Surface) 88.9 86.4

Set forth below are particularly suitable highly neutralized polymer compositions for forming thermoplastic layers. The following commercially available materials were used in the below examples:

-   -   A-C® 5120 ethylene acrylic acid copolymer with an acrylic acid         content of 15%, A-C® 5180 ethylene acrylic acid copolymer with         an acrylic acid content of 20%, A-C® 395 high density oxidized         polyethylene homopolymer, and A-C® 575 ethylene maleic anhydride         copolymer, commercially available from Honeywell; CB23 high-cis         neodymium-catalyzed polybutadiene rubber, commercially available         from Lanxess Corporation; CA1700 Soya fatty acid, CA1726         linoleic acid, and CA1725 conjugated linoleic acid, commercially         available from Chemical Associates; Century® 1107 highly         purified isostearic acid mixture of branched and straight-chain         C18 fatty acid, commercially available from Arizona Chemical;         Clarix® 011370-01 ethylene acrylic acid copolymer with an         acrylic acid content of 13% and Clarix® 011536-01 ethylene         acrylic acid copolymer with an acrylic acid content of 15%,         commercially available from A. Schulman Inc.; Elvaloy® AC 1224         ethylene-methyl acrylate copolymer with a methyl acrylate         content of 24 wt %, Elvaloy® AC 1335 ethylene-methyl acrylate         copolymer with a methyl acrylate content of 35 wt %, Elvaloy® AC         2116 ethylene-ethyl acrylate copolymer with an ethyl acrylate         content of 16 wt %, Elvaloy® AC 3427 ethylene-butyl acrylate         copolymer having a butyl acrylate content of 27 wt %, and         Elvaloy® AC 34035 ethylene-butyl acrylate copolymer having a         butyl acrylate content of 35 wt %, commercially available         from E. I. du Pont de Nemours and Company; Escor® AT-320         ethylene acid terpolymer, commercially available from ExxonMobil         Chemical Company; Exxelor® VA 1803 amorphous ethylene copolymer         functionalized with maleic anhydride, commercially available         from ExxonMobil Chemical Company; Fusabond® N525         metallocene-catalyzed polyethylene, Fusabond® N416 chemically         modified ethylene elastomer, Fusabond® C190 anhydride modified         ethylene vinyl acetate copolymer, and Fusabond® P614         functionalized polypropylene, commercially available from E. I.         du Pont de Nemours and Company; Hytrel® 3078 very low modulus         thermoplastic polyester elastomer, commercially available         from E. I. du Pont de Nemours and Company; Kraton® FG 1901 GT         linear triblock copolymer based on styrene and ethylene/butylene         with a polystyrene content of 30% and Kraton® FG1924GT linear         triblock copolymer based on styrene and ethylene/butylene with a         polystyrene content of 13%, commercially available from Kraton         Performance Polymers Inc.; Lotader® 4603, 4700 and 4720, random         copolymers of ethylene, acrylic ester and maleic anhydride,         commercially available from Arkema Corporation; Nordel® IP 4770         high molecular weight semi-crystalline EPDM rubber, commercially         available from The Dow Chemical Company; Nucrel® 9-1, Nucrel®         599, Nucrel® 960, Nucrel® 0407, Nucrel® 0609,

Nucrel® 1214, Nucrel® 2906, Nucrel® 2940, Nucrel® 30707, Nucrel® 31001, and Nucrel® AE acid copolymers, commercially available from E. I. du Pont de Nemours and Company; Primacor® 3150, 3330, 59801, and 59901 acid copolymers, commercially available from The Dow Chemical Company; Royaltuf® 498 maleic anhydride modified polyolefin based on an amorphous EPDM, commercially available from Chemtura Corporation; Sylfat® FA2 tall oil fatty acid, commercially available from Arizona Chemical; Vamac® G terpolymer of ethylene, methylacrylate and a cure site monomer, commercially available from E. I. du Pont de Nemours and Company; and XUS 60758.08L ethylene acrylic acid copolymer with an acrylic acid content of 13.5%, commercially available from The Dow Chemical Company.

Various compositions were melt blended using components as given in Table 18 below. The compositions were neutralized by adding a cation source in an amount sufficient to neutralize, theoretically, 110% of the acid groups present in components 1 and 3, except for example 72, in which the cation source was added in an amount sufficient to neutralize 75% of the acid groups. Magnesium hydroxide was used as the cation source, except for example 68, in which magnesium hydroxide and sodium hydroxide were used in an equivalent ratio of 4:1. In addition to components 1-3 and the cation source, example 71 contains ethyl oleate plasticizer.

The relative amounts of component 1 and component 2 used are indicated in Table 18 below, and are reported in wt %, based on the combined weight of components 1 and 2. The relative amounts of component 3 used are indicated in Table 18 below, and are reported in wt %, based on the total weight of the composition.

TABLE 18 Example Component 1 wt % Component 2 wt % Component 3 wt % 1 Primacor 5980I 78 Lotader 4603 22 magnesium oleate 41.6 2 Primacor 5980I 84 Elvaloy AC 1335 16 magnesium oleate 41.6 3 Primacor 5980I 78 Elvaloy AC 3427 22 magnesium oleate 41.6 4 Primacor 5980I 78 Elvaloy AC 1335 22 magnesium oleate 41.6 5 Primacor 5980I 78 Elvaloy AC 1224 22 magnesium oleate 41.6 6 Primacor 5980I 78 Lotader 4720 22 magnesium oleate 41.6 7 Primacor 5980I 85 Vamac G 15 magnesium oleate 41.6 8 Primacor 5980I 90 Vamac G 10 magnesium oleate 41.6 8.1 Primacor 59901 90 Fusabond 614 10 magnesium oleate 41.6 9 Primacor 5980I 78 Vamac G 22 magnesium oleate 41.6 10 Primacor 5980I 75 Lotader 4720 25 magnesium oleate 41.6 11 Primacor 5980I 55 Elvaloy AC 3427 45 magnesium oleate 41.6 12 Primacor 5980I 55 Elvaloy AC 1335 45 magnesium oleate 41.6 12.1 Primacor 5980I 55 Elvaloy AC 34035 45 magnesium oleate 41.6 13 Primacor 5980I 55 Elvaloy AC 2116 45 magnesium oleate 41.6 14 Primacor 5980I 78 Elvaloy AC 34035 22 magnesium oleate 41.6 14.1 Primacor 59901 80 Elvaloy AC 34035 20 magnesium oleate 41.6 15 Primacor 5980I 34 Elvaloy AC 34035 66 magnesium oleate 41.6 16 Primacor 5980I 58 Vamac G 42 magnesium oleate 41.6 17 Primacor 59901 80 Fusabond 416 20 magnesium oleate 41.6 18 Primacor 5980I 100 — — magnesium oleate 41.6 19 Primacor 5980I 78 Fusabond 416 22 magnesium oleate 41.6 20 Primacor 59901 100 — — magnesium oleate 41.6 21 Primacor 59901 20 Fusabond 416 80 magnesium oleate 41.6 21.1 Primacor 59901 20 Fusabond 416 80 magnesium oleate 31.2 21.2 Primacor 59901 20 Fusabond 416 80 magnesium oleate 20.8 22 Clarix 011370 30.7 Fusabond 416 69.3 magnesium oleate 41.6 23 Primacor 59901 20 Royaltuf 498 80 magnesium oleate 41.6 24 Primacor 59901 80 Royaltuf 498 20 magnesium oleate 41.6 25 Primacor 59901 80 Kraton FG1924GT 20 magnesium oleate 41.6 26 Primacor 59901 20 Kraton FG1924GT 80 magnesium oleate 41.6 27 Nucrel 30707 57 Fusabond 416 43 magnesium oleate 41.6 28 Primacor 59901 80 Hytrel 3078 20 magnesium oleate 41.6 29 Primacor 59901 20 Hytrel 3078 80 magnesium oleate 41.6 30 Primacor 5980I 26.8 Elvaloy AC 34035 73.2 magnesium oleate 41.6 31 Primacor 5980I 26.8 Lotader 4603 73.2 magnesium oleate 41.6 32 Primacor 5980I 26.8 Elvaloy AC 2116 73.2 magnesium oleate 41.6 33 Escor AT-320 30 Elvaloy AC 34035 52 magnesium oleate 41.6 Primacor 5980I 18 34 Nucrel 30707 78.5 Elvaloy AC 34035 21.5 magnesium oleate 41.6 35 Nucrel 30707 78.5 Fusabond 416 21.5 magnesium oleate 41.6 36 Primacor 5980I 26.8 Fusabond 416 73.2 magnesium oleate 41.6 37 Primacor 5980I 19.5 Fusabond N525 80.5 magnesium oleate 41.6 38 Clarix 011536- 26.5 Fusabond N525 73.5 magnesium oleate 41.6 01 39 Clarix 011370- 31 Fusabond N525 69 magnesium oleate 41.6 01 39.1 XUS 60758.08L 29.5 Fusabond N525 70.5 magnesium oleate 41.6 40 Nucrel 31001 42.5 Fusabond N525 57.5 magnesium oleate 41.6 41 Nucrel 30707 57.5 Fusabond N525 42.5 magnesium oleate 41.6 42 Escor AT-320 66.5 Fusabond N525 33.5 magnesium oleate 41.6 43 Nucrel 21 Fusabond N525 79 magnesium oleate 41.6 2906/2940 44 Nucrel 960 26.5 Fusabond N525 73.5 magnesium oleate 41.6 45 Nucrel 1214 33 Fusabond N525 67 magnesium oleate 41.6 46 Nucrel 599 40 Fusabond N525 60 magnesium oleate 41.6 47 Nucrel 9-1 44.5 Fusabond N525 55.5 magnesium oleate 41.6 48 Nucrel 0609 67 Fusabond N525 33 magnesium oleate 41.6 49 Nucrel 0407 100 — — magnesium oleate 41.6 50 Primacor 5980I 90 Fusabond N525 10 magnesium oleate 41.6 51 Primacor 5980I 80 Fusabond N525 20 magnesium oleate 41.6 52 Primacor 5980I 70 Fusabond N525 30 magnesium oleate 41.6 53 Primacor 5980I 60 Fusabond N525 40 magnesium oleate 41.6 54 Primacor 5980I 50 Fusabond N525 50 magnesium oleate 41.6 55 Primacor 5980I 40 Fusabond N525 60 magnesium oleate 41.6 56 Primacor 5980I 30 Fusabond N525 70 magnesium oleate 41.6 57 Primacor 5980I 20 Fusabond N525 80 magnesium oleate 41.6 58 Primacor 5980I 10 Fusabond N525 90 magnesium oleate 41.6 59 — — Fusabond N525 100 magnesium oleate 41.6 60 Nucrel 0609 40 Fusabond N525 20 magnesium oleate 41.6 Nucrel 0407 40 61 Nucrel AE 100 — — magnesium oleate 41.6 62 Primacor 5980I 30 Fusabond N525 70 CA1700 soya fatty 41.6 acid magnesium salt 63 Primacor 5980I 30 Fusabond N525 70 CA1726 linoleic 41.6 acid magnesium salt 64 Primacor 5980I 30 Fusabond N525 70 CA1725 41.6 conjugated linoleic acid magnesium salt 65 Primacor 5980I 30 Fusabond N525 70 Century 1107 41.6 isostearic acid magnesium salt 66 A-C 5120 73.3 Lotader 4700 26.7 oleic acid 41.6 magnesium salt 67 A-C 5120 73.3 Elvaloy 34035 26.7 oleic acid 41.6 magnesium salt 68 Primacor 5980I 78.3 Lotader 4700 21.7 oleic acid 41.6 magnesium salt and sodium salt 69 Primacor 5980I 47 Elvaloy AC34035 13 — — A-C 5180 40 70 Primacor 5980I 30 Fusabond N525 70 Sylfat FA2 41.6 magnesium salt 71 Primacor 5980I 30 Fusabond N525 70 oleic acid magnesium salt 31.2 ethyl oleate 10 72 Primacor 5980I 80 Fusabond N525 20 sebacic acid 41.6 magnesium salt 73 Primacor 5980I 60 — — — — A-C 5180 40 74 Primacor 5980I 78.3 — — oleic acid 41.6 A-C 575 21.7 magnesium salt 75 Primacor 5980I 78.3 Exxelor VA 1803 21.7 oleic acid 41.6 magnesium salt 76 Primacor 5980I 78.3 A-C 395 21.7 oleic acid 41.6 magnesium salt 77 Primacor 5980I 78.3 Fusabond C190 21.7 oleic acid 41.6 magnesium salt 78 Primacor 5980I 30 Kraton FG 1901 70 oleic acid 41.6 magnesium salt 79 Primacor 5980I 30 Royaltuf 498 70 oleic acid 41.6 magnesium salt 80 A-C 5120 40 Fusabond N525 60 oleic acid 41.6 magnesium salt 81 Primacor 5980I 30 Fusabond N525 70 erucic acid 41.6 magnesium salt 82 Primacor 5980I 30 CB23 70 oleic acid 41.6 magnesium salt 83 Primacor 5980I 30 Nordel IP 4770 70 oleic acid 41.6 magnesium salt 84 Primacor 5980I 48 Fusabond N525 20 oleic acid 41.6 A-C 5180 32 magnesium salt 85 Nucrel 2806 22.2 Fusabond N525 77.8 oleic acid 41.6 magnesium salt 86 Primacor 3330 61.5 Fusabond N525 38.5 oleic acid 41.6 magnesium salt 87 Primacor 3330 45.5 Fusabond N525 20 oleic acid 41.6 Primacor 3150 34.5 magnesium salt 88 Primacor 3330 28.5 — — oleic acid 41.6 Primacor 3150 71.5 magnesium salt 89 Primacor 3150 67 Fusabond N525 33 oleic acid 41.6 magnesium salt 90 Primacor 5980I 55 Elvaloy AC 34035 45 oleic acid magnesium salt 31.2 ethyl oleate 10

Solid spheres of each composition were injection molded, and the solid sphere COR, compression, Shore D hardness, and Shore C hardness of the resulting spheres were measured after two weeks. The results are reported in Table 19 below. The surface hardness of a sphere is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the sphere or on surface defects, such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface, care must be taken to insure that the sphere is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for all hardness measurements and is set to record the maximum hardness reading obtained for each measurement. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand. The weight on the durometer and attack rate conform to ASTM D-2240.

TABLE 19 Solid Solid Solid Solid Sphere Sphere Sphere Sphere Ex. COR Compression Shore D Shore C 1 0.845 120 59.6 89.2 2 * * * * 3 0.871 117 57.7 88.6 4 0.867 122 63.7 90.6 5 0.866 119 62.8 89.9 6 * * * * 7 * * * * 8 * * * * 8.1 0.869 127 65.3 92.9 9 * * * * 10 * * * * 11 * * * * 12 0.856 101 55.7 82.4 12.1 0.857 105 53.2 81.3 13 * * * * 14 0.873 122 64.0 91.1 14.1 * * * * 15 * * * * 16 * * * * 17 0.878 117 60.1 89.4 18 0.853 135 67.6 94.9 19 * * * * 20 0.857 131 66.2 94.4 21 0.752  26 34.8 57.1 21.1 0.729  9 34.3 56.3 21.2 0.720  2 33.8 55.2 22 * * * * 23 * * * * 24 * * * * 25 * * * * 26 * * * * 27 * * * * 28 * * * * 29 * * * * 30 **  66 42.7 65.5 31 0.730  67 45.6 68.8 32 ** 100 52.4 78.2 33 0.760  64 43.6 64.5 34 0.814  91 52.8 80.4 35 * * * * 36 * * * * 37 * * * * 38 * * * * 39 * * * * 39.1 * * * * 40 * * * * 41 * * * * 42 * * * * 43 * * * * 44 * * * * 45 * * * * 46 * * * * 47 * * * * 48 * * * * 49 * * * * 50 * * * * 51 0.873 121 61.5 90.2 52 0.870 116 60.4 88.2 53 0.865 107 57.7 84.4 54 0.853  97 53.9 80.2 55 0.837  82 50.1 75.5 56 0.818  66 45.6 70.7 57 0.787  45 41.3 64.7 58 0.768  26 35.9 57.3 59 * * * * 60 * * * * 61 * * * * 62 * * * * 63 * * * * 64 * * * * 65 * * * * 66 * * * * 67 * * * * 68 * * * * 69 * * * * 70 * * * * 71 * * * * 72 * * * * 73 * * * * 74 * * * * 75 * * * * 76 * * * * 77 * * * * 78 * * * * 79 * * * * 80 * * * * 81 * * * * 82 * * * * 83 * * * * 84 * * * * 85 * * * * 86 * * * * 87 * * * * 88 * * * * 89 * * * * 90 * * * * * not measured ** sphere broke during measurement

When ninnerical lower limits and ninnerical upper limits are set forth herein, it is contemplated that any combination of these values may be used.

All patents, publications, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains. 

What is claimed is:
 1. A golf ball having a weight of 1.620 oz. or less, an outer diameter of at least 1.700 inches, and a CoR of at least 0.700, comprising: a core comprising a rubber composition and having a first specific gravity that is greater than 1.0 g/cc; and an intermediate layer having an outer diameter of about 1.680 inches or greater and consisting of a foamed polyurethane composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising a polyurethane composition and having a third specific gravity that is greater than 1.0 g/cc; and wherein the first specific gravity is less than the third specific gravity.
 2. The golf ball of claim 1, wherein the core has a diameter of 1.580 inches or greater.
 3. The golf ball of claim 2, wherein the foamed polyurethane composition of the intermediate layer is a thermoset material.
 4. The golf ball of claim 3, wherein the polyurethane composition of the cover layer is a thermoset material.
 5. The golf ball of claim 3, wherein the polyurethane composition of the cover layer is a thermoplastic material.
 6. The golf ball of claim 2, wherein the foamed polyurethane composition of the intermediate layer is a thermoplastic material.
 7. The golf ball of claim 2, wherein the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL), being greater than the H_(inner surface of IL) to provide a positive hardness gradient.
 8. The golf ball of claim 7, wherein the core has an outer surface hardness (R_(inner core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.
 9. The golf ball of claim 7, wherein the core has an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being equal to or less than the H_(core center) to provide a zero to negative hardness gradient.
 10. The golf ball of claim 2, wherein the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the H_(inner surface of IL) to provide a zero to negative hardness gradient.
 11. The golf ball of claim 7, wherein H_(outer surface of IL) is greater than 50 Shore D.
 12. The golf ball of claim 10, wherein H_(outer surface of IL) is 50 Shore D or less.
 13. The golf ball of claim 2, wherein the second specific gravity differs from each of the first specific gravity and the third specific gravity by from about 0.20 g/cc to about 0.30 g/cc.
 14. The golf ball of claim 2, wherein the intermediate layer has an outer diameter of about 1.69 inches or greater.
 15. A golf ball having a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, and a CoR of at least 0.700, comprising: an inner core layer comprising a rubber composition and having a first specific gravity that is less than 1.2 g/cc; and an outer core layer comprising an unfoamed highly neutralized (HNP) composition and having a second specific gravity of less than 1.0 g/cc; an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.
 16. The golf ball of claim 15, wherein the inner core layer has a diameter of 0.500 inches or greater, the outer core layer has an outer diameter of 1.62 inches or less, and the cover layer has an outer diameter of 1.720 inches or greater.
 17. The golf ball of claim 16, wherein the first specific gravity and third specific gravity are substantially similar and less than the second specific gravity and fourth specific gravity.
 18. The golf ball of claim 17, wherein the second specific gravity and fourth specific gravity are substantially similar.
 19. The golf ball of claim 18, wherein the first specific gravity and third specific gravity differ by up to about 0.35 g/cc.
 20. The golf ball of claim 19, wherein the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient.
 21. The golf ball of claim 20, wherein the outer core layer has an outer surface hardness (H_(core surface)) and the inner core layer has a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a negative hardness gradient.
 22. The golf ball of claim 20, wherein the outer core layer has an outer surface hardness (H_(core surface)) and the inner core layer has a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.
 23. The golf ball of claim 19, wherein the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being equal to or less than the H_(inner surface of IL) to provide a zero to negative hardness gradient.
 24. The golf ball of claim 20, wherein H_(outer surface of IL) is greater than 50 Shore D.
 25. The golf ball of claim 23, wherein H_(outer surface of IL) is 50 Shore D or less.
 26. The golf ball of claim 19, wherein the intermediate layer has an outer diameter that is greater than 1.68 inches.
 27. The golf ball of claim 19, wherein the intermediate layer has an outer diameter of 1.69 inches or greater.
 28. A golf ball having a weight of 1.620 oz. or less, an outer diameter of at least 1.750 inches, and a CoR of at least 0.700, comprising: a core comprising a rubber composition and having a first specific gravity of greater than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; an inner cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a fourth specific gravity that is less than 1.0 g/cc.
 29. The golf ball of claim 28, wherein the core layer has a diameter of 1.50 inches or less.
 30. The golf ball of claim 28, wherein the first specific gravity and fourth specific gravity differ by up to 0.10 and the second specific gravity and the third specific gravity differ by up to 0.35.
 31. The golf ball of claim 30, wherein the intermediate layer has an outer surface hardness (R_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient.
 32. The golf ball of claim 31, wherein the core has a surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.
 33. The golf ball of claim 28, wherein the intermediate layer has an outer diameter that is greater than 1.68 inches.
 34. The golf ball of claim 28, wherein the intermediate layer has an outer diameter of 1.69 inches or greater.
 35. A golf ball having a weight of 1.620 oz. or less, an outer diameter of at least 1.720 inches, and a CoR of at least 0.700, comprising: a core comprising an HNP composition and having a first specific gravity that is less than 1.0 g/cc; and an intermediate layer having an outer diameter of 1.680 or greater and consisting of a foamed HNP composition and having a second specific gravity that is less than 1.0 g/cc; and a cover layer comprising an ionomer composition and having a third specific gravity that is less than 1.0 g/cc; and
 36. The golf ball of claim 35, wherein the core has a diameter of 1.600 inches or greater; and the cover has an outer diameter of 1.720 inches or greater.
 37. The golf ball of claim 35, wherein the first specific gravity and third specific gravity are substantially similar and greater than the second specific gravity.
 38. The golf ball of claim 36, wherein the first specific gravity differs from each of the second specific gravity and the third specific gravity by up to about 0.35 g/cc.
 39. The golf ball of claim 38, wherein the intermediate layer has an outer surface hardness (H_(outer surface of IL)) and an inner surface hardness (H_(inner surface of IL)), the H_(outer surface of IL) being greater than the H_(inner surface of IL) to provide a positive hardness gradient.
 40. The golf ball of claim 39, wherein the core has an outer surface hardness (H_(core surface)) and a center hardness (H_(core center)), the H_(core surface) being greater than the H_(core center) to provide a positive hardness gradient.
 41. The golf ball of claim 35, wherein the intermediate layer has an outer diameter that is greater than 1.68 inches.
 42. The golf ball of claim 35, wherein the intermediate layer has an outer diameter of 1.69 inches or greater 